Print head assembly for use in fused deposition modeling system

ABSTRACT

A print head assembly that includes a print head carriage and multiple, replaceable print heads that are configured to be removably retained in receptacles of the print head carriage.

CROSS-REFERENCE TO RELATED APPLICATION(S)

Reference is hereby made to co-filed U.S. patent application Ser. No.12/976,152, filed on Dec. 22, 2010, and published as U.S. PublicationNo. 2012/0164330; to co-filed U.S. patent application Ser. No.12/976,176, filed on Dec. 22, 2010, and published as U.S. PublicationNo. 2012/0161350; to co-filed U.S. patent application Ser. No.12/976,204, filed on Dec. 22, 2010, and published as U.S. PublicationNo. 2012/0162305; and to co-filed U.S. Design Pat. application No.29/381,753, filed on Dec. 22, 2010, and issued as U.S. Design Pat. No.D660,353.

BACKGROUND

The present disclosure relates to additive manufacturing systems forbuilding three-dimensional (3D) parts with layer-based, additivemanufacturing techniques. In particular, the present disclosure relatesto print head assemblies for use in fused deposition modeling systems.

A fused deposition modeling system is used to build a 3D part or modelfrom a digital representation of the 3D part in a layer-by-layer mannerby extruding a flowable part material. The part material is extrudedthrough an extrusion tip carried by an extrusion head, and is depositedas a sequence of roads on a substrate in an x-y plane. The extruded partmaterial fuses to previously deposited modeling material, and solidifiesupon a drop in temperature. The position of the extrusion head relativeto the substrate is then incremented along a z-axis (perpendicular tothe x-y plane), and the process is then repeated to form a 3D partresembling the digital representation.

Movement of the extrusion head with respect to the substrate isperformed under computer control, in accordance with build data thatrepresents the 3D part. The build data is obtained by initially slicingthe digital representation of the 3D part into multiple horizontallysliced layers. Then, for each sliced layer, the host computer generatesa build path for depositing roads of modeling material to form the 3Dpart.

In fabricating 3D parts by depositing layers of a modeling material,supporting layers or structures are typically built underneathoverhanging portions or in cavities of objects under construction, whichare not supported by the part material itself. A support structure maybe built utilizing the same deposition techniques by which the partmaterial is deposited. The host computer generates additional geometryacting as a support structure for the overhanging or free-space segmentsof the 3D part being formed. Support material is then deposited from asecond nozzle pursuant to the generated geometry during the buildprocess. The support material adheres to the modeling material duringfabrication, and is removable from the completed 3D part when the buildprocess is complete.

SUMMARY

An aspect of the present disclosure is directed to a print head assemblyfor use in a fused deposition modeling system. The print head assemblyincludes a carriage frame configured to be retained by a gantrymechanism of the fused deposition modeling system, and a receptacle. Thereceptacle is supported from the carriage frame such that the receptacleis moveable relative to the carriage frame along at least one axis,where the receptacle is configured to securely retain a removable printhead in a manner that prevents the retained print head from movingrelative to the receptacle during operation of the fused depositionmodeling system.

Another aspect of the present disclosure is directed to a print headassembly for use in a fused deposition modeling system, where the printhead assembly includes a carriage frame configured to be retained by agantry mechanism of the fused deposition modeling system. The print headassembly also includes a receptacle having a base portion and a lid. Thebase portion is supported from the carriage frame and configured toreceive a removable print head, where the base portion includes analignment feature configured to engage with a reciprocal alignmentfeature of the received print head. The lid is configured to closeagainst the base portion to retain the received print head at leastpartially within the receptacle.

Another aspect of the present disclosure is directed to a fuseddeposition modeling system. The fused deposition modeling systemincludes a platen, a gantry configured to move relative to the platen, acarriage frame secured to the gantry, and a control board secured to thecarriage frame. The fused deposition modeling system also includes aplurality of receptacles suspended from the carriage frame such that theplurality of receptacles are moveable relative to the carriage framealong at least one axis independently of each other. Each of theplurality of receptacles are configured to securely retain a removableprint head, and are also configured to relay electrical power andcommunications between the control board and the retained print head.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top perspective view of a fused deposition modeling system,which includes a print head assembly of the present disclosure.

FIG. 2 is a front, top perspective view of the print head assembly,which includes a carriage, a pair of removable print heads, and a pairof voice coil mechanisms.

FIG. 3 is a rear, top perspective view of the print head assembly.

FIG. 4 is an expanded rear, top perspective view of the print headassembly, illustrating an upper flexure of the carriage.

FIG. 5 is a front, bottom perspective view of the print head assembly,illustrating a lower flexure of the carriage.

FIG. 6 is a bottom view of the lower flexure of the carriage.

FIG. 7 is a bottom view of a portion of the print head assembly,illustrating an engagement of the lower flexure with the carriage.

FIG. 8 is a front view of the print head assembly, illustrating theoperation of voice coil mechanisms of the print head assembly.

FIG. 9 is a rear view of the print head assembly, further illustratingthe operation of the voice coil mechanisms.

FIG. 10 is a front, top perspective view of the carriage without theprint heads.

FIG. 11 is a front view of the carriage.

FIG. 12 is a side view of a receptacle of the carriage, illustrating anoperation of a lid of the receptacle.

FIG. 13 is a sectional view of Section 13-13 taken in FIG. 11,illustrating one of the voice coil mechanisms.

FIG. 14 is a sectional view of Section 14-14 taken in FIG. 12, furtherillustrating the voice coil mechanisms.

FIG. 15 is a front, top perspective view of one of the print headspositioned above a receptacle of the carriage, illustrating a processfor loading or inserting the print head into the receptacle.

FIG. 16 is a bottom view of the print head.

FIG. 17 is an exploded, front perspective view of the print head.

FIG. 18 is a bottom view of a housing cover of the print head.

FIG. 19 is a top view of a housing body of the print head.

FIG. 20 is a front, top perspective view of a motor of the print head.

FIG. 21 is a front, top perspective view of a liquefier pump assembly ofthe print head.

FIG. 22 is a rear, top perspective view of the liquefier pump assembly.

FIG. 23 is an exploded front, top perspective view of the liquefier pumpassembly.

FIG. 24 is a front, bottom perspective view of a tip end of theliquefier pump assembly.

FIG. 25 is a sectional view of Section 25-25 taken in FIG. 21, furtherillustrating the liquefier pump assembly.

FIG. 26 is a flow diagram of a method for assembling the print head.

FIG. 27 is a flow diagram of a method for assembling the liquefier pumpassembly.

DETAILED DESCRIPTION

The present disclosure is directed to a print head assembly for use in afused deposition modeling system. The print head assembly includes amoveable, print head carriage and multiple, replaceable print heads thatare configured to be removably retained by the print head carriage. Asdiscussed below, the print head carriage includes a carriage frame andat least one, and more desirably two or more print head buckets orreceptacles that are configured to receive and retain the removableprint heads.

The receptacles may be supported by the carriage frame in a manner thatprevents or otherwise restricts the receptacles from moving relative tothe carriage frame along an axis or plane (e.g., a horizontal plane). Inone embodiment, the receptacles are also supported by the carriage framein a manner that allows the receptacles to move relative to the carriagealong at least one axis (e.g., along a vertical axis), providing asingle degree of freedom for movement. Additionally, the receptaclesdesirably lock the received print heads to prevent their shiftingrelative to the receptacles. While the print heads are retained in thereceptacles of the print head carriage, the fused disposition modelingsystem may build 3D parts and support structures using the fuseddeposition modeling technique.

The present disclosure is also directed to one or more voice coilmechanisms of the print head assembly, where each voice coil mechanismis configured to raise and lower a receptacle and the received printhead relative to the carriage frame. This toggling technique allows thefused deposition modeling system to switch between part materialextrusion and support material extrusion with precise control of thevertical movements.

As discussed below, each voice coil mechanism may include one or moremagnet sets disposed between ferromagnetic plates, where the magnetset(s) are configured to generate magnetic fields. Each voice coilmechanism may also include a voice coil disposed within the generatedmagnetic fields and configured to move relative to the generatedmagnetic fields based on an intensity and direction of an electricalcurrent induced through the voice coil. In one embodiment, the voicecoil is retained by the receptacle and the magnet set(s) are retained bythe carriage frame. In this embodiment, the movement of the voice coilrelative to the generated magnetic fields may move the receptacle andreceived print head relative to the carriage frame to toggle the printhead between one or more raised and lowered elevations.

The present disclosure is also directed to a removable print head foruse with the print head carriage and the fused deposition modelingsystem, and a method of assembling the print head. The print head isconfigured to be received and retained in the receptacle of the printhead carriage, and has a liquefier pump assembly that may include aself-aligning feature to align a received filament with a liquefierportion of the liquefier pump assembly. In one embodiment, the printhead may also include a flow pathway configured to direct an air flowthrough the print head. As discussed below, these arrangements allow theprint head to efficiently feed, melt, and extrude successive portions offilaments of part and support materials.

FIG. 1 is a perspective view of system 10, which is an example of afused deposition modeling system that may incorporate the print headassembly of the present disclosure. Suitable fused deposition modelingsystems for system 10 include those developed by Stratasys, Inc., EdenPrairie, Minn. As shown, system 10 includes build chamber 12, platen 14,gantry 16, print head carriage 18, and consumable assemblies 20 and 22.

Build chamber 12 is an enclosed environment that contains platen 14 forbuilding a 3D part or model 24 and a corresponding support structure 26with part and support consumable materials (e.g., thermoplasticmaterials). Build chamber 12 is desirably heated to reduce the rate atwhich the part and support materials solidify after being extruded anddeposited (e.g., to reduce distortions and curling). In alternativeembodiments, build chamber 12 may be omitted and/or replaced withdifferent types of build environments. For example, 3D part 24 andsupport structure 26 may be built in a build environment that is open toambient conditions or may be enclosed with alternative structures (e.g.,flexible curtains). The build environment may also be heatable in avariety of manners (e.g., with heated circulating air, heat lamps, andthe like).

Platen 14 is a gantry-moveable platform on which 3D part 24 and supportstructure 26 are built, and moves along a vertical z-axis based onsignals provided from a computer-operated controller (referred to ascontroller 28). Controller 28 is one or more processor-basedcontrollers, which may communicate with build chamber 12, platen 14,gantry 16, and carriage 18 over communication line 30. While illustratedas a single signal line, communication line 30 may include one or moresignal lines, allowing controller 28 to communicate with variouscomponents of system 10, such as build chamber 12, platen 14, gantry 16,and carriage 18. Furthermore, while illustrated outside of system 10,controller 28 and communication line 30 may be internal components tosystem 10.

Gantry 16 is a guide-rail, gantry mechanism configured to move carriage18 in a horizontal x-y plane above build chamber 12 based on signalsprovided from controller 28 (via communication line 30). The horizontalx-y plane is a plane defined by an x-axis and a y-axis, where thex-axis, the y-axis, and the z-axis are orthogonal to each other. In analternative embodiment, platen 14 may be configured to move in thehorizontal x-y plane within build chamber 12, and carriage 18 may beconfigured to move along the z-axis. Other similar arrangements may alsobe used such that one or both of platen 14 and carriage 18 are moveablerelative to each other.

In the shown embodiment, when mounted in gantry 16, the front side ofcarriage 18 faces the rear side of system 10. For ease of discussion,the following disclosure is made with reference to particularorientations within an x-y-z Cartesian coordinate system, based on theorientation of carriage 18 and its corresponding print head assembly.However, the print head assembly of the present disclosure mayalternatively be positioned and operated in a variety of differentorientations and/or coordinate systems.

Carriage 18 is supported by gantry 16 for building 3D parts (e.g., 3Dpart 24) and corresponding support structures (e.g., support structure26) on platen 14 in a layer-by-layer manner, based on signals providedfrom controller 28. In the shown embodiment, carriage 18 is retainedwithin cowling 31, which is a casing (e.g., a plastic and/or metalliccasing) that laterally extends around carriage 18 to protect carriage18, while also allowing a user to access to carriage 18. As discussedbelow, carriage 18 is configured to receive one or more removable printheads, where the print heads are each configured to receive and meltsuccessive portions of part and support material filaments.

Consumable assemblies 20 and 22 are removable and replaceable containerdevices configured to retain supplies of the part and support materialsfor building 3D parts (e.g., 3D part 24) and support structures (e.g.,support structure 26), and may be respectively loaded into bays 20 a and22 a of system 10. In the shown embodiment, consumable assembly 20includes container portion 32, guide tube 34, and print head 36, wherecontainer portion 32 is mountable within bay 20 a and print head 36 isinserted or otherwise loaded into carriage 18. Guide tube 34interconnects container portion 32 and print head 36 to supplysuccessive segments of a part material filament from container portion32 to print head 36.

Correspondingly, consumable assembly 22 includes container portion 38,guide tube 40, and printer head 42, where container portion 38 ismountable within bay 22 a and print head 42 is inserted or otherwiseloaded into carriage 18, adjacent to print head 36. Guide tube 40interconnects container portion 38 and print head 42 to supplysuccessive segments of a support material filament from containerportion 38 to print head 42.

In the shown example, suitable assemblies for consumable assemblies 20and 22 include those disclosed in Swanson, U.S. Patent ApplicationPublication No. 2010/0283172 and International Publication No.WO2009/088995, which are incorporated by reference in their entiretiesto the extent that they do not conflict with the present disclosure. Asdisclosed in these references, print heads 36 and 42 may be provided assubcomponents of consumable assemblies 20 and 22. When containerportions 32 and 38 are respectively loaded to bays 20 a and 22 a, printheads 36 and 42 may be manipulated and loaded into carriage 18.

The combination of carriage 18 and print heads 36 and 42 arecollectively referred to herein as print head assembly 43. Accordingly,after print head 36 is inserted or otherwise loaded into carriage 18,successive portions of a part material (e.g., a part material filament)may be fed from container portion 32 to print head 36 through guide tube34. Similarly, after print head 42 is inserted or otherwise loaded intocarriage 18, successive portions of a support material (e.g., a supportmaterial filament) may be fed to print head 42 from container portion 38through guide tube 40.

As the part and support materials are selectively fed to print heads 36and 42, gantry 16 may move carriage 18 (and the retained print heads 36and 42) around in the horizontal x-y plane above build chamber 12. Printhead 36 thermally melts the successive portions of the received partmaterial, thereby allowing the molten part material to be extruded anddeposited on to platen 14 to build 3D part 24. Similarly, print head 42thermally melts the successive portions of the support material, therebyallowing the molten support material to be extruded and deposited on toplaten 14 to build support structure 26.

The extruded part and support materials are deposited onto platen 14 tobuild 3D part 24 and support structure 26 in a layer-based manner usingthe fused deposition modeling technique. Support structure 26 isdesirably deposited to provide vertical support along the z-axis foroverhanging regions of the layers of 3D part 24. After the buildoperation is complete, the resulting 3D part 24 and support structure 26may be removed from build chamber 12, and support structure 26 may beremoved from 3D part 24. 3D part 23 may then undergo one or moreadditional post-processing steps, such as the surface-treatmentprocesses disclosed in Priedeman, et al., U.S. Patent ApplicationPublication No. 2005/0173838 and U.S. Patent Application Publication No.2008/0169585.

The following discussion of system 10 is made with reference toconsumable assemblies 20 and 22 that include print heads (i.e., printheads 36 and 42) as subcomponents of the consumable assemblies. However,in alternative embodiments, print heads 36 and 42 may be removable printheads that are separate from container portions 32 and 38 and/or guidetubes 34 and 40. In these embodiments, suitable assemblies (e.g.,spooled containers) for consumable assemblies 20 and 22 include thosedisclosed in Swanson, U.S. Patent Application Publication No.2010/0283172 and International Publication No. WO2009/088995, as well asthose disclosed in Swanson et al., U.S. Pat. No. 6,923,634; Comb et al.,U.S. Pat. No. 7,122,246; and Taatjes et al, U.S. Patent ApplicationPublication Nos. 2010/0096485 and 2010/0096489.

FIGS. 2-9 illustrate print head assembly 43, showing carriage 18 in usewith print heads 36 and 42. Carriage 18 and print heads 36 and 42 aredesirably low-weight components. The use of low-weight components forprint head assembly 43 reduces the mass that gantry 16 (shown in FIG. 1)is required to move around in the horizontal x-y plane. This reducedmass correspondingly reduces the inertial forces that are generated whenmoving print head assembly 43 around in the horizontal x-y plane (e.g.,in raster patterns), thereby improving the response time control ofgantry 16 and also reducing wear on the subcomponents of gantry 16.

As shown in FIG. 2, carriage 18 includes carriage frame 44, print headbuckets or receptacles 46 and 48, control board 50, voice coilmechanisms 52 and 54 (located below receptacles 46 and 48), and coolingunits 56 and 58. Carriage frame 44 is a rigid frame member that isoperably secured to gantry 16 (shown in FIG. 1) with multiples fasteners(e.g., screws 59). Carriage frame 44 may be molded or cast from one ormore metallic and/or plastic materials.

Receptacles 46 and 48 are the components of carriage 18 thatrespectively retain print heads 36 and 42, and may also be molded orcast from one or more metallic and/or plastic materials. Print head 36includes cartridge assembly 60 and liquefier pump assembly 62, where arear portion of cartridge assembly 60 is retained within receptacle 46and liquefier pump assembly 62 extends downward from a front portion ofcartridge assembly 60. Similarly, print head 42 includes cartridgeassembly 64 and liquefier pump assembly 66, where a rear portion ofcartridge assembly 64 is retained within receptacle 48 and liquefierpump assembly 66 extends downward from a front portion of cartridgeassembly 64. Liquefier pump assemblies 62 and 66 respectively includetip ends 62 a and 66 a, and outlet vents 62 b and 66 b.

In the shown embodiment, print heads 36 and 42 are mirror images of eachother. This reduces the risk of inserting the incorrect print head intoa given receptacle. In comparison, in the shown embodiment, receptacles46 and 48 are identical or substantially identical, allowing the samemold to be used to manufacture the components of both receptacles 46 and48. In alternative embodiments, print heads 36 and 42, and receptacles46 and 48 may exhibit different designs such that print heads 36 and 42may be received and retained by receptacles 46 and 48 in the mannersdiscussed below.

Receptacle 46 includes base portion 68 and lid 70, where lid 70 ishingedly connected to an upper rear section of base portion 68 withhinge connection 72, allowing lid 70 to open and close relative to baseportion 68. Prior to use in system 10 (shown in FIG. 1), cartridgeassembly 60 (of print head 36) may be inserted or otherwise loaded intobase portion 68, and lid 70 may be closed down over the rear portion ofcartridge assembly 60 to secure print head 36 to receptacle 46.

Lid 70 includes lock clamps 74 and pinch actuator 76. When closedagainst base portion 68 (as shown in FIG. 2), lock clamps 74 engage baseportion 68 to prevent lid 70 from unintentionally opening. When a userdesires to open lid 70, the user may squeeze pinch actuator 76, whichdisengages lock clamps 74 from base portion 68, thereby allowing theuser to then open lid 70.

Receptacle 48 includes base portion 78 and lid 80, where lid 80 ishingedly connected to an upper rear section of base portion 78 withhinge connection 82, allowing lid 80 to open and close relative to baseportion 78. Prior to use in system 10, cartridge assembly 64 (of printhead 42) may be inserted or otherwise loaded into base portion 78 andlid 80 may be closed down over the rear portion of cartridge assembly 64to secure print head 42 to receptacle 48.

Lid 80 includes lock clamps 84 and pinch actuator 86. When closedagainst base portion 78 (as shown in FIG. 2), lock clamps 84 engage baseportion 78 to prevent lid 80 from unintentionally opening in the samemanner as discussed above for lock clamps 74. When a user desires toopen lid 80, the user may squeeze pinch actuator 86, which disengageslock clamps 84 from base portion 78, thereby allowing the user to thenopen lid 80.

Receptacles 46 and 48 desirably prevent print heads 36 and 42 fromshifting around within receptacles 46 and 48 while lids 70 and 80 areclosed. System 10 is configured to build 3D part 24 and supportstructure 26 with high-resolution features. To attain suchhigh-resolution features, print heads 36 and 42 are desirably locked tocarriage frame 44 in a manner that prevents unintentional shifting ofprint heads 36 and 42 relative to carriage frame 44 in the horizontalx-y plane. Otherwise, even small amounts of unintentional horizontalshifting by either of print heads 36 and 42 may result in depositionroad errors in the formed layers of 3D part 24 and support structure 26.

In current commercial fused deposition modeling systems, such as thosecommercially available from Stratasys, Inc., Eden Prairie, Minn., theextrusion or print heads are secured to the moveable gantry carriagesusing screws or other fasteners. These print heads are typically notuninstalled from the moveable gantry carriages other than formaintenance, cleaning, or other similar purposes. In such situations,after being reinstalled to the moveable gantry carriages, the printheads are typically calibrated before each build run to reduce the riskof deposition road errors. Since the print heads are securely installedto the moveable gantry carriages, they pose little risk of shiftingrelative to the moveable gantry carriages during the build runs.

In comparison, print heads 36 and 42 are intended to be readily removedand replaced when their consumable materials are exhausted. Thisreplaceable nature of print heads 36 and 42 poses an added challenge tomaintaining proper registration between print heads 36 and 42 andcarriage frame 44 during build runs. This challenge is further increasedsince print heads 36 and 42 (and receptacles 46 and 48) are alsomoveable along the vertical z-axis via voice coil mechanisms 52 and 54.

Accordingly, as discussed below, carriage 18 is configured to receivemultiple, replaceable print heads print heads 36 and 42, and to securelylock the received print heads 36 and 42 to prevent their unintentionalshifting relative to carriage frame 44 in the horizontal x-y plane. Inparticular, when lids 70 and 80 are closed, receptacles 46 and 48securely lock print heads 36 and 42, which prevents print heads 36 and42 from moving relative to receptacles 46 and 48 in any direction.

Receptacles 46 and 48 themselves are suspended from carriage frame 44 ina manner that allows controlled movement of receptacles 46 and 48 (andprint heads 36 and 42) relative to carriage frame 44 along the verticalz-axis via voice coil mechanisms 52 and 54, while also preventingunintentional movement of receptacles 46 and 48 (and print heads 36 and42) relative to carriage frame 44 in the horizontal x-y plane. Forexample, receptacles 46 and 48 may be suspended from carriage frame 44with upper flexure 88, located behind the upper rear sections ofreceptacles 46 and 48, as discussed below. As used herein, phrases suchas “preventing movement or shifting of the print heads” and the like areintended to encompass insubstantial amounts of movement or shifting asis understood by those skilled in the art, such that the movements orshifting of the print heads do not substantially affect the resolutionsof the 3D parts or support structures.

Voice coil mechanisms 52 and 54 are toggle mechanisms configured tocontrollably move receptacles 46 and 48 (and print heads 36 and 42)upward and downward along the vertical z-axis, independently of eachother. As discussed in Leavitt, U.S. Pat. No. 7,625,200, togglemechanisms, such as voice coil mechanisms 52 and 54, allow print heads36 and 42 to each switch between a lowered, active state for extruding amaterial and a raised, passive state. In one embodiment, as discussedbelow, voice coil mechanisms 52 and 54 each include one or more magnetsets (not shown in FIG. 2) disposed between magnetic plates (not shownin FIG. 2), where the magnet set(s) are configured to generate magneticfields.

Voice coil mechanisms 52 and 54 may each also include a voice coil (notshown in FIG. 2) disposed within the generated magnetic fields andconfigured to move relative to the generated magnetic fields based on anintensity and direction of an electrical current induced through thevoice coil. As discussed below, the movement of the voice coil relativeto the generated magnetic fields may move receptacle 46 or 48 andreceived print head 36 or 42 relative to carriage frame 44 to toggleprint head 36 or 42 between one or more raised and lowered elevations.Voice coil mechanisms 52 and 54 may also include electrical connections(e.g., cables, not shown) to interfaces 89 of control board 50 toreceive electrical power from control board 50 for inducing theelectrical currents through the voice coils.

Control board 50 is a printed circuit board or other similar devicesecured to the rear side of carriage frame 44. As shown, control board50 includes interfaces 90 and 91, where interfaces 90 may be operablyconnected to communication line 30 (shown in FIG. 1), power sources,and/or other electrical ports within system 10 (not shown) with the useof electrical cables and/or wireless connections (not shown). Forexample, interfaces 90 may relay electrical power from system 10 toprint heads 36 and 42, control board 50, voice coil mechanisms 52 and 54(via interfaces 89), and cooling units 56 and 58. Interfaces 90 may alsoallow controller 28 (shown in FIG. 1) to direct the operation of printheads 36 and 42, voice coil mechanisms 52 and 54, and cooling units 56and 58, as discussed below.

Interfaces 91 are electrical interfaces that allow electrical power tobe relayed from control board 50 to cooling units 56 and 58 overadditional electrical connections (e.g., cables, not shown). As alsodiscussed below, control board 50 may include one or more positionencoders for tracking or otherwise monitoring the positions of printheads 36 and 42 relative to carriage 18 and control board 50 (e.g.,vertical positions).

Cooling units 56 and 58 are fan-based units secured to gantry 16 and/orcarriage frame 44 (e.g., with screws 92). Cooling units 56 and 58 areconfigured to create and direct air flows into print heads 36 and 42.For example, cooling unit 56 may draw air into cartridge assembly 60 ofprint head 36, where the air is then directed downward through liquefierpump assembly 62 and out of outlet vents 62 b. Similarly, cooling unit58 may draw air into cartridge assembly 64 of print head 42, where theair is then directed downward through liquefier pump assembly 66 and outof outlet vents 66 b. The forced air flows cool the internal componentsof print heads 36 and 42 and prevent the part and support materials fromprematurely melting. In alternative embodiments, other types of coolingunits may be used for cooling units 56 and 58, which may be fan-basedunits or non-fan-based units (e.g., refrigeration-based units).

Lids 70 and 80 of receptacles 46 and 48 also include electricalinterfaces 94 and 96, which are located on the outer surfaces of lids 70and 80, adjacent to the top rear side of carriage 18. As shown in FIG.3, control board 50 also includes interfaces 98 and 100, which are portsconfigured to communicate with electrical interfaces 94 and 96,respectively, over electrical connections (e.g., cables, not shown).This arrangement allows control board 50 to relay electrical power andcommunication information to and between print heads 36 and 42 anditself. Control board 50 may be secured to carriage frame 44 with screws102 or other similar fasteners.

In the shown embodiment, carriage 18 also includes upper flexure 88,which is a flexible metallic or plastic member that is secured tocarriage frame 44. As discussed below, upper flexure 88 and a lowerflexure (not shown in FIG. 3) support receptacles 46 and 48 in a mannerthat prevents receptacles 46 and 48 (and the retained print heads 36 and42) from moving horizontally, while allowing a limited range of verticalmovement due to the flexing of upper flexure 88 and the lower flexure.

As shown in FIG. 4, upper flexure 88 is secured to carriage frame 44with screws 104 a-104 c or other similar fasteners. This couplingprevents upper flexure suspension 88 from moving relative to carriageframe 44 other than by flexing. The spaced apart locations of screws 104a-104 c separates upper flexure suspension 88 into flexure segments 106and 108, where flexure segment 106 is located between screws 104 a and104 b, and flexure segment 108 is located between screws 104 b and 104c. Flexure segments 106 and 108 are each configured to flex upward,downward, or a combination of upward and downward relative to carriageframe 44, independently of each other.

Base portion 68 of receptacle 46 includes tab member 110 extendingrearwardly from the body of base portion 68, and is secured to flexuresegment 106 with screw 112 or other similar fastener. Screw 112 couplesreceptacle 46 to flexure segment 106, which allows receptacle 46 andprint head 36 to move upwards and downwards (via voice coil mechanism52, shown in FIGS. 2 and 3) relative to carriage frame 44 with theflexing of flexure segment 106 (and the lower flexure, not shown in FIG.4). This coupling also prevents lateral movement of receptacle 46 andprint head 36 in the horizontal x-y plane relative to carriage frame 44,as well as preventing roll, pitch, and yaw movements.

Base portion 78 of receptacle 48 includes tab member 114 extendingrearwardly from the body of base portion 78, and is secured to flexuresegment 108 with screw 116 or other similar fastener. Screw 116 couplesreceptacle 48 to flexure segment 108, which allows receptacle 48 andprint head 42 to move upwards and downwards (via voice coil mechanism54, shown in FIGS. 2 and 3) relative to carriage frame 44 with theflexing of flexure segment 108 (and the lower flexure, not shown in FIG.4). This coupling also prevents lateral movement of receptacle 48 andprint head 42 in the horizontal x-y plane relative to carriage frame 44,as well as preventing roll, pitch, and yaw movements.

During assembly of carriage 18, upper flexure 88 may be positioned oncarriage frame 44 as shown in FIG. 4, and screws 104 a-104 c may beinserted through openings upper flexure 88 and into carriage frame 44 tosecure upper flexure 88 to carriage frame 44. Tab members 110 and 114may be coupled to flexure segments 106 and 108 with screws 112 and 116to retain base portions 68 and 78 to upper flexure 88.

As shown in FIG. 5, which is a bottom perspective view of print headassembly 43, receptacles 46 and 48 respectively include lower extensions118 and 120. Lower extension 118 extends below base portion 68 andretains a portion of voice coil mechanism 52 (e.g. a voice coil, notshown in FIG. 5). Similarly, lower extension 120 extends below baseportion 78 and retains a portion of voice coil mechanism 54 (e.g. avoice coil, not shown in FIG. 5). As further shown in FIG. 5, the frontside of control board 50 includes sensor arrays 122 a and 122 b, whichare subcomponents of a pair of optical encoder assemblies that areconfigured to measure positions of receptacles 46 and 48 (e.g., verticalpositions), as discussed below.

Carriage 18 also includes lower flexure 124, which, in the shownembodiment, has an H-shape geometry. Lower flexure 124 is a flexiblemetallic or plastic member disposed vertically between the bottomsurfaces of base portions 68 and 78 and the bottom portion of carriageframe 44.

As shown in FIG. 6, lower flexure 124 includes central segment 126extending along the y-axis, and arms 128 a-128 d, where arms 128 a and128 b are front arms that extend in opposing directions along the x-axisfrom a front end of central segment 126, and arms 128 c and 128 d arerear arms that extend in opposing directions along the x-axis from arear end of central segment 126.

Central segment 126 includes openings 130 and 132 respectively at thefront and rear ends of central segment 126. Openings 130 and 132 areattachment points for securing central segment 126 to carriage frame 44(shown in FIGS. 2-5) with fasteners (e.g., screws, not shown). Arms 128a-128 d respectively include openings 134 a-134 d and pin slots 136a-136 d. Lower flexure 124 has a symmetrical geometry, allowing eitherend to face forward. This arrangement increases the ease in assemblingcarriage 18 by allowing lower flexure 124 to be secured to base portions68 and 78, and to carriage frame 44 regardless of its orientation.

As shown in FIG. 7, lower flexure 124 is secured to base portions 68 and78 at arms 128 a-128 d. In particular, arm 128 a is aligned with a frontsection of base portion 68 with alignment pins 138 that extend throughpin slots 136 a. Arm 128 a is secured to base portion 68 with screw 140or other similar fastener, which extends through opening 134 a in arm128 a. Correspondingly, arm 128 b is aligned with a front section ofbase portion 78 with alignment pins 142 that extend through pin slots136 b. Arm 128 b is secured to base portion 78 with screw 144 or othersimilar fastener, which extends through opening 134 b in arm 128 b.

Arm 128 c is aligned with a rear section of base portion 68 withalignment pins 146 that extend through pin slots 136 c (both partiallyobstructed by carriage frame 44 in FIG. 7). Arm 128 c is secured to baseportion 68 with screw 148 or other similar fastener, which extendsthrough opening 134 c in arm 128 c. Arm 128 d is correspondingly alignedwith a rear section of base portion 78 with alignment pins 150 thatextend through pin slots 136 d (both partially obstructed by carriageframe 44 in FIG. 7). Arm 128 d is secured to base portion 78 with screw152 or other similar fastener, which extends through opening 134 d inarm 128 d.

In addition, lower flexure 124 may be aligned with and secured tocarriage frame 44 at bottom openings 154 a and 154 b of carriage frame44 with screws and/or pins (not shown) or other similar fasteners.Openings 154 a and 154 b extend along the y-axis and are aligned withopenings 130 and 132 of lower flexure 124. Accordingly, during assemblyof carriage 18, lower flexure 124 may be positioned along carriage frame44 as shown in FIG. 7, and screws and/or pins may be inserted throughopenings 154 a and 154 b of carriage frame 44, and through openings 130and 132 of lower flexure 124 to secure central segment 126 (shown abovein FIG. 6) to carriage frame 44. Base portions 68 and 78 may then bepositioned on to carriage frame 44 and arms 128 a-128 d of lower flexure124 may be secured to base portions 68 and 78. This secures lowerflexure 124 between carriage frame 44 and base portions 68 and 78,thereby supporting base portions 68 and 78 from carriage frame 44. Asdiscussed above, base portions 68 and 78 may also be further supportedfrom carriage frame 44 with upper flexure 88 (shown above in FIGS. 3 and4).

Arms 128 a-128 d are each configured to flex upward, downward, or acombination of upward and downward along the vertical z-axis relative tocarriage frame 44, where arms 128 a and 128 c (secured to base portion68) may flex together and arms 128 b and 128 d (secured to base portion78) may flex together. Accordingly, arms 128 a and 128 c (along withflexure segment 106 of upper flexure 88, shown in FIG. 4) allowreceptacle 46 and print head 36 to move upwards and downwards (via voicecoil mechanism 52) relative to carriage frame 44. These couplings alsoprevent movement of receptacle 46 and print head 36 in the horizontalx-y plane relative to carriage frame 44, as well as preventing roll,pitch, and yaw movements. Similarly, arms 128 b and 128 d (along withflexure segment 108 of upper flexure 88, shown in FIG. 4) allowreceptacle 48 and print head 42 to move upwards and downwards (via voicecoil mechanism 54) relative to carriage frame 44. These couplings alsoprevent movement of receptacle 48 and print head 42 in the horizontalx-y plane relative to carriage frame 44, as well as preventing roll,pitch, and yaw movements.

While illustrated with a pair of flexures (i.e., upper flexure 88 andlower flexure 124) that provide three connection points for eachreceptacle 46 and 48, carriage 18 may alternatively include additionalflexures and/or additional connection points to further prevent movementof receptacles 46 and 48 relative to carriage frame 44 in the horizontalx-y plane. For example, carriage 18 may alternatively include a pair ofupper flexures and a pair of lower flexures for each receptacle, whereeach upper and lower flexure is operably secured to carriage frame 44.This provides four connection points for each receptacle, therebyfurther preventing horizontal movement, while allowing controlledvertical movement with voice coil mechanisms 52 and 54.

In additional alternative embodiments, one or both of upper flexure 88and lower flexure 124 may be replaced with alternative mechanisms thatare configured to suspend base portions 68 and 78 from carriage frame44, while also preventing or restricting movement of base portions 68and 78 in the horizontal x-y plane relative to carriage frame 44 (andpreventing roll, pitch, and yaw movements). For example, upper flexure88 may be replaced with a rigid member that pivotably interconnects baseportions 68 and 78 with carriage frame 44 in a seesaw or lever-basedmanner.

In this embodiment, the rigid member may be pivotably connected tocarriage frame 44 at the location of screw 104 b (shown in FIG. 4), suchas with a pin joint. Tab members 110 and 114 of base portions 68 and 78may then be secured to the rigid member (e.g., pivotably secured) at thelocations of screws 112 and 116 (shown in FIG. 4). Accordingly, voicecoil mechanism 52 may toggle receptacle 46 and print head 36 upwardwhile voice coil mechanism 54 toggles receptacle 48 and print head 42downward, which pivots the rigid member around its pivotable connectionwith carriage frame 44. The pivoting action allows print heads 36 and 42to move vertically, while also preventing or restricting their movementsin the horizontal x-y plane.

In further alternative embodiments, the rigid member may be replacedwith a pair of independent rigid members, which may be pivotablyconnected to carriage frame 44, and separately connected to tab members110 and 114 of base portions 68 and 78. This arrangement allows printheads 36 and 42 to be toggled independently of each other. In yetfurther alternative embodiments, carriage 18 may include vertical linearbearings or bushings to prevent or restrict horizontal movement of baseportions 68 and 78 relative to carriage frame 44, while also allowingvertical movement.

As further shown in FIG. 7, carriage frame 44 also includes a first pairof openings 154 below base portion 68, and a second pair of openings 156below base portion 78. Only a single opening 154 and a single opening156 are visible in FIG. 7. The second of openings 154 and 156 are hiddenunder arms 128 c and 128 d of lower flexure 124. As discussed below,openings 154 and 156 may receive screws or other similar fasteners (notshown) for securing carriage frame 44 to gantry 16 (shown in FIG. 1)along with screws 59, where the screws are insertable into openings 154and 156 from above through base portions 68 and 78.

FIG. 8 illustrates the toggling of receptacles 46 and 48 with the use ofvoice coil mechanisms 52 and 54. As shown, voice coil mechanism 52includes front plate 158 and voice coil mechanism 54 includes frontplate 160. In the shown embodiment, front plates 158 and 160 areprovided as a single plate that extends across the front sides of voicecoil mechanisms 52 and 54, and which is secured to carriage frame 44with screw 161 or other similar fastener. Front plates 158 and 160 areferromagnetic plates that retain the magnet sets (not shown in FIG. 8)for voice coil mechanisms 52 and 54, as discussed below.

In the example shown in FIG. 8, print head 42 and receptacle 48 arepositioned at a lower elevation along the vertical z-axis compared toprint head 36 and receptacle 46. This is illustrated by the relativeelevations of tip ends 62 a and 66 a, where tip end 62 a is located atraised elevation 162 and tip end 66 a is located at lowered elevation164. Accordingly, print head 42 is in an active state for extruding thesupport material and print head 36 is in a passive state in which printhead 36 does not extrude the part material.

Suitable distances between raised elevation 162 and lowered elevation164 (referred to as distance 165) include at least about 0.5millimeters, with particularly suitable distances 165 ranging from about1.0 millimeters to about 3.0 millimeters, and with even moreparticularly suitable distances 165 ranging from about 1.3 millimetersto about 2.0 millimeters. The terms “about” and “substantially” are usedherein with respect to measurable values and ranges due to expectedvariations known to those skilled in the art (e.g., limitations andvariabilities in measurements). The raised elevation of tip end 62 arelative to tip end 66 a prevents tip end 62 a from contacting theformed layers of 3D part 24 (shown in FIG. 1) or support structure 26(shown in FIG. 1) while carriage 18 is moved around in the horizontalx-y plane above build chamber 12 (shown in FIG. 1).

FIG. 9 is a rear view of print head assembly 43, illustrating print head36 being toggled downward from raised elevation 162 and print head 42being toggled upward from lower elevation 164 in a simultaneous manner,as illustrated by arrows 166 a and 166 b. While receptacle 48 and printhead 42 are in the lowered, active state (as shown above in FIG. 8),flexure segment 108 of upper flexure 88 and arms 128 b and 128 d oflower flexure 124 (shown above in FIGS. 5-7) are flexed downward alongthe vertical z-axis. Correspondingly, while receptacle 46 and print head36 are in the raised, passive state, flexure segment 106 of upperflexure 88, and arms 128 a and 128 c of lower flexure 124 (shown inFIGS. 5-7) are un-flexed and level. Upper flexure 88 and lower flexure124 accordingly restrict the movements of receptacles 46 and 48 andprint heads 36 and 42 to upward and downward directions that aresubstantially along the vertical z-axis relative to carriage frame 44.

After a given layer of support structure 26 is completed, controller 28(shown in FIG. 1) may direct voice coil mechanism 54 to raise receptacle48 and print head 42 upward along the vertical z-axis from loweredelevation 164 to raised elevation 162 (or other suitable raisedelevation along the vertical z-axis), as illustrated by arrow 166 b.Flexure segment 108 of upper flexure 88 and arms 128 b and 128 d oflower flexure 124 accordingly flex upward along with receptacle 48 andprint head 42 to reach un-flexed and level states.

Controller 28 may also direct voice coil mechanism 52 to lowerreceptacle 46 and print head 36 downward along the vertical z-axis fromraised elevation 162 to lowered elevation 164 (or other suitable loweredelevation along the vertical z-axis), as illustrated by arrow 166 a.Flexure segment 106 of upper flexure 88 and arms 128 a and 128 c oflower flexure 124 accordingly flex downward along with receptacle 46 andprint head 36.

At this point in the build process, print head 36 is in an active statefor extruding the part material and print head 42 is in a passive statein which print head 42 does not extrude the support material. The raisedelevation of tip end 66 a relative to tip end 62 a prevents tip end 66 afrom contacting the formed layers of 3D part 24 or support structure 26while carriage 18 is moved around in the horizontal x-y plane abovebuild chamber 12.

After a given layer(s) of 3D part 24 is completed, controller 28 maythen direct voice coil mechanism 52 to raise receptacle 46 and printhead 36 upward along the vertical z-axis from lowered elevation 164 toraised elevation 162 (or other suitable raised elevation along thevertical z-axis). Controller 28 may also direct voice coil mechanism 54to lower receptacle 48 and print head 42 downward along the verticalz-axis from raised elevation 162 to lowered elevation 164 (or othersuitable lowered elevation along the vertical z-axis). This togglingplaces print head 42 back into the lowered, active state and placesprint head 36 back into the raised, passive state.

Print heads 36 and 42 may then continue to toggle interchangeablybetween the active and passive states with the use of voice coilmechanisms 52 and 54, where movement of print heads 36 and 42 arerestricted to directions substantially along the vertical z-axis byupper flexure 88 and lower flexure 124. In alternative embodiments, thetoggling process may be performed with the use of a single voice coilmechanism. For example, print head 36 may be fixed at a given elevation(voice coil mechanism 52 may be omitted), and voice coil mechanism 54may move print head 42 between a lowered elevation and a raisedelevation that are respectively below and above the fixed elevation ofprint head 36. Platen 14 may then be raised and lowered during thetoggling process to accommodate the different elevations of print heads36 and 42. However, the use of two voice coil mechanisms (i.e., voicecoil mechanisms 52 and 54) allows the tip positions of print heads 36and 42 (i.e., at tip ends 62 a and 66 a) to be independently calibrated,such as when one of print heads 26 and 42 needs to be replaced duringthe middle of a build run.

As further shown in FIG. 9, the voice coil mechanism 52 includes rearplate 167 and voice coil mechanism 54 includes rear plate 168. In theshown embodiment, rear plates 167 and 168 are also provided as a singleplate that extends across the rear sides of voice coil mechanisms 52 and54, and which is secured to carriage frame 44 with screw 169 or othersimilar fastener. Rear plates 167 and 168 are ferromagnetic plates thatretain the magnet sets (not shown in FIG. 9) for voice coil mechanisms52 and 54, along with front plates 158 and 160.

FIGS. 10-12 illustrate carriage frame 44 and receptacles 46 and 48, withprint heads 36 and 42, control board 50, and cooling units 56 and 58omitted. As shown in FIG. 10, base portion 68 of receptacle 46 hasdimensions that are configured to receive and retain the rear portion ofcartridge assembly 60. Similarly, base portion 78 of receptacle 48 hasdimensions that are configured to receive and retain the rear portion ofcartridge assembly 64.

Base portions 68 and 78 include vent openings 170 and 172, which areopenings through the lateral walls of base portions 68 and 78. Theoutside vent openings 170 and 172 allow air from cooling units 56 and 58(shown above in FIGS. 2, 3, 5, and 8) to be directed toward print heads36 and 42, respectively. The inside vent openings 170 and 172, whichface each other, are included to allow base portions 68 and 78 to beidentical, thereby allowing a single base portion to be manufactured foruse as base portions 68 and 78.

Lid 80 is depicted in FIG. 10 in an open state. As shown, lid 80 alsoincludes bridge member 173, which connects the parallel tabs of pinchactuator 86. Bridge member 173 is configured to bias when pinch actuator86 is squeezed, thereby allowing latch clamps 84 to disconnect from baseportion 78.

Lid 80 also includes circuit board 174, which is secured to the insidesurface of lid 80 with screws 176 or other similar fasteners. Circuitboard 174 is a printed circuit board or other similar device coupled toelectrical interface 96 (shown in FIGS. 2-4 and 9), and includeselectrical contact 178. As discussed below, electrical contact 178 isconfigured to interface with print head 42 when print head 42 isinserted into base portion 78 with lid 80 closed. This allows electricalpower and communication to be relayed to and between print head 42 andcontrol board 50 (via circuit board 174, electrical interface 96, andelectrical contact 178). As discussed below, lid 70 includes a similararrangement for relaying electrical power and communication to andbetween print head 36 and control board 50. In alternative embodiments,circuit board 174 and the corresponding circuit board of lid 70 may bereplaced with different types of electrical circuits, such as one ormore flexible circuits. In these embodiments, the flexible circuits maydirectly connect between control board 50 and lids 70 and 80 (i.e.,electrical interfaces 94 and 96 may be omitted).

Lids 70 and 80 also include recessed lips 180 and 182, where recessedlip 180 is disposed between latch clamps 74 and recessed lip 182 isdisposed between latch clamps 84. Recessed lips 180 and 182 havegeometries configured to mate with cartridge assemblies 60 and 64 whenprint heads 36 and 42 are inserted in base portions 68 and 70, asillustrated above in FIGS. 2, 3, and 8.

Base portions 68 and 78 may each include one or more alignment featuresconfigured engage with reciprocating alignment features of print heads36 and 42. For example, base portion 68 includes alignment cones 184,and base portion 78 includes alignment cones 186. Alignment cones 184and 186 upward protrusions that engage with reciprocating slots in printheads 36 and 42 (not shown in FIG. 10 or 11) for providing three-pointalignments. Base portion 68 also includes slot 188, through which screw140 may extend to secure lower flexure 124 (shown in FIGS. 5-7) to baseportion 68. Similarly, base portion 78 also includes slot 190, throughwhich screw 144 may extend to secure lower flexure 124 to base portion78.

When lids 70 and 80 are closed, print heads 36 and 42 are presseddownward into base portions 68 and 78 to fully engage alignment cones184 an 186. This secures print heads 36 and 42 within receptacles 68 and78 and prevents horizontal and vertical movement of print heads 36 and42 relative to receptacles 68 and 78, respectively (as well aspreventing roll, pitch, and yaw movements). In alternative embodiments,print heads 36 and 42 may include alignment cones and base portions 68and 78 may include the reciprocating slots.

As further shown in FIG. 10, base portion 68 includes a pair of flooropenings 192 and base portion 78 includes a pair of floor openings 194(only a single floor opening 192 and a single floor opening 194 arefully visible in FIG. 10). Floor openings 192 and 194 are aligned withopenings 154 and 156 of carriage frame 44 (shown in FIG. 7). Flooropenings 192 and 194 provide access points for inserting screws or otherfasteners into openings 154 and 156 to secure carriage frame 44 togantry 16 (shown above in FIG. 1) after supporting receptacles 46 fromcarriage frame 44 with upper flexure 88 and lower flexure 124. Thisreduces the time and effort required to secure carriage 18 to gantry 16by allowing carriage 18 to be assembled prior to being mounted to gantry16.

Base portions 68 and 78 also include floor gaps 196 and 198, which aretop-down openings in the floors of base portions 68 and 78. Lowerextensions 118 and 120 are accessible from above through floor gaps 196and 198. As such, the voice coils (not shown) of voice coil mechanisms52 and 54 may be inserted into lower extensions 118 and 120 throughfloor gaps 196 and 198 to mount the voice coils in lower extensions 118and 120.

As shown in FIG. 11, base portions 68 and 78 also include rear wallopenings 200 and 202, which are U″-shaped openings configured to matewith print heads 36 and 42 (rear wall opening 202 is partially visiblein FIG. 10). As discussed below, control board 50 (shown above in FIGS.2-5, 8, and 9) also includes encoder sensors 204 and 206 (illustratedwith broken lines in FIG. 11) located adjacent to, and accessiblethrough, rear wall openings 200 and 202, respectively. Examples ofsuitable sensors for encoder sensors 204 and 206 include rotary hallsensors (e.g., 2D hall sensors) and the like.

FIG. 12 is a side view of receptacle 46, illustrating the lockingengagement between base portion 68 and lid 70 of receptacle 46. Asdiscussed above, in the shown embodiment, receptacles 46 and 48 areidentical to each other. As such, the following side view discussion ofreceptacle 46 is also applicable to receptacle 48.

As shown in FIG. 12, lid 70 includes bridge member 208, which connectsthe parallel tabs of pinch actuator 76. Bridge member 208 is configuredto bias when pinch actuator 76 is squeezed, thereby allowing latchclamps 74 to disconnect from base portion 68. As further shown, thefront side of base portion 68 includes a pair of latch hooks 210 andbeveled surfaces 212 (only a single latch hook 210 and beveled surface212 are shown in FIG. 12). Latch hooks 210 are the features of baseportion 68 that latch clamps 74 of lid 70 engage with to lock lid 70 tobase portion 68.

A user may open lid 70 by squeezing pinch actuator 76, as illustrated byarrows 214. This biases latch clamps 74 in the direction of arrow 216due to bridge member 208, where the biasing releases latch clamps 74from latch hooks 212. The release of latch clamps 74 unlocks lid 70 frombase portion 68, which allows lid 70 to be opened by pivoting aroundhinge connection 72, as illustrated by arrow 218.

After print head 36 is inserted or otherwise loaded into base portion68, the user may then close lid 70, by pivoting lid 70 around hingeconnection 72 in a direction that is opposite of arrow 218. When latchclamps 74 of lid 70 reaches beveled surfaces 212, the increasing slopesof beveled surfaces 212 in a direction along the y-axis increasinglybias latch clamps 74 in the direction of arrow 216 (in a similar mannerto squeezing pinch actuator 76). Upon passing below beveled surfaces212, latch clamps 74 snap lock with latch hooks 210, thereby locking lid70 closed against base portion 68.

When closed and locked with latch clamps 74 and latch hooks 210,receptacle 46 securely locks and retains print head 36 in a manner thatprevents print head 36 from moving relative to receptacle 46 in anydirection. As discussed above, this arrangement is suitable forpreventing unintentional horizontal and vertical shifting, as well aspreventing roll, pitch, and yaw movements.

FIG. 13 is a sectional view of Section 13-13 taken in FIG. 11, whichillustrates voice coil mechanism 52 and optical encoder assembly 220. Asshown, carriage 18 includes optical encoder assembly 220, which is areflective optical encoder for receptacle 46 that detects the upward anddownward movements of base portion 68. Carriage 18 also includes asecond optical encoder assembly (not shown), which is a reflectiveoptical encoder for receptacle 48 that detects the upward and downwardmovements of base portion 78. As such, optical encoder assembly 220measures the vertical positions of receptacle 46 and print head 36, andthe second optical encoder assembly measures the vertical positions ofreceptacle 48 and print head 42.

Examples of suitable optical encoder assemblies for optical encoderassembly 220 and the second optical encoder assembly include thosedisclosed in Batchelder, U.S. Provisional Patent Application No.61/312,737, entitled “Incremental Optical Encoder”, and which isincorporated by reference in its entirety to the extent that it does notconflict with the present disclosure. Optical sensor assembly 220includes sensor array 122 a and sensor target 222. As discussed above,sensor array 122 a is retained on the front surface of control board 50,and includes knife-edge electronics for operating optical sensorassembly 220 (e.g., light emitters, photoreceptors, and processors).

Sensor target 222 is a panel secured to the rear side of base portion68. In the shown embodiment, sensor target 222 includes a reflective orlight-colored surface (e.g., reflective sheet metal, silicon minor, andthe like) and a non-reflective or dark surface or opening, where thereflective surface is located either above or below the non-reflectivesurface or opening. In either arrangement, the position of receptacle 46along the vertical z-axis may be determined based on the locations ofthe surfaces of sensor target 222 relative to sensor array 122 a.

The second optical encoder assembly for receptacle 48 may function inthe same manner as optical encoder assembly 220. As discussed above,sensor array 122 b (shown in FIG. 5) is retained on the front surface ofcontrol board 50, and includes knife-edge electronics for operating thesecond optical sensor assembly (e.g., light emitters, photoreceptors,and processors). The second optical encoder assembly also includes asensor target (not shown) secured to the rear side of base portion 78.The position of receptacle 48 along the vertical z-axis may thereby bedetermined based on the locations of the surfaces of the sensor targetrelative to sensor array 122 b.

As further shown in FIG. 13, voice coil mechanism 52 includes uppermagnets 224 and 226, and lower magnets 228 and 230, which are two setsof magnets disposed between front plate 158 and rear plate 167. Uppermagnet 224 and lower magnet 228 may be secured to front plate 158 suchthat upper magnet 224 is located vertically above lower magnet 228, andupper magnet 226 and lower magnet 230 may be secured to rear plate 167such that upper magnet 226 is located vertically above lower magnet 230.

Upper magnets 224 and 226 are oriented to generate an upper magneticfield with field lines in a first direction (e.g., in the direction ofarrow 231 a), and which may close through rear plate 167. Lower magnets228 and 230 are oriented to generate a lower magnetic field with fieldlines oriented in a second direction (e.g., in the direction of arrow231 b) that are opposite in polarity from the upper magnetic field, andwhich may close through front plate 158. Upper magnets 224 and 226 andlower magnets 228 and 230 may alternatively be positioned in theirreciprocating orientations, such that the upper magnetic field extendsin the direction of arrow 231 b and the lower magnetic field extends inthe direction of arrow 231 a.

As shown, upper magnets 224 and 226 face each other, and lower magnets228 and 230 face each other. In the shown embodiment, front plate 158,rear plate 167, upper magnets 224 and 226, and lower magnets 228 and 230are retained by carriage frame 44 and do not move with receptacle 46.Voice coil mechanism 52 also includes voice coil 232, which is a coil ofwire or other coiled assembly that is secured to and supported by lowerextension 118 of receptacle 46. This allows receptacle 46 to move withvoice coil 232 relative to carriage frame 44.

FIG. 14 is a sectional view of Section 14-14 taken in FIG. 12. As shownin FIG. 14, voice coil mechanism 54 includes upper magnet 234, lowermagnet 236, and rear magnets (not shown) corresponding to magnets 226and 230 (shown in FIG. 13), which are disposed between front plate 160and rear plate 168 (shown above in FIG. 9). As such, in the shownembodiment, front plate 160, rear plate 168, upper magnet 234, lowermagnet 236, and the respective rear magnets are retained by carriageframe 44 and do not move with receptacle 48. Voice coil mechanism 54includes voice coil 238, which is a second coil of wire or other coiledassembly that is secured to and supported by lower extension 120 ofreceptacle 48, thereby allowing receptacle 48 to move with voice coil238 relative to carriage frame 44.

In the shown embodiment, voice coil mechanisms 52 and 54 may function asvoice coil actuators, where receptacle 48 is illustrated in FIG. 14 at alowered vertical elevation relative to receptacle 46 (corresponding tothe view shown above in FIG. 8). Accordingly, with respect to voice coilmechanism 52, receptacle 46 (and print head 36) may be toggled upward ordownward by inducing an electrical current through voice coil 232, wherethe upward or downward direction depends on the rotational direction ofthe electrical current that passes through voice coil 232. Inparticular, the direction of movement is dictated by the force appliedto voice coil 232, which is generally at a right angle to the rotationaldirection of the electrical current induced through voice coil 232 andto the generated magnetic fields.

For example, if an electrical current is passed in a first rotationaldirection around voice coil 232, the magnetic fields generated by uppermagnets 224 and 226 and lower magnets 228 and 230 force voice coil 232upward relative to carriage frame 44. Because voice coil 232 is securedto lower extension 118 of receptacle 46, the upward force on voice coil232 correspondingly forces receptacle 46 and print head 36 to moveupward relative to carriage frame 44. Alternatively, if an electricalcurrent is passed in a second and opposite rotational direction aroundvoice coil 232, the magnetic fields generated by upper magnets 224 and226 and lower magnets 228 and 230 force voice coil 232 downward, therebymoving receptacle 46 and print head 36 downward relative to carriageframe 44.

Voice coil mechanism 54 may function in the same manner as voice coilmechanism 52 to move receptacle 48 and print head 42 upward and downwardrelative to carriage frame 44 based on electrical currents inducedthrough voice coil 238. The use of voice coils 232 and 238 in thismanner provide fine-positioning control of the vertical movements forreceptacles 46 and 48, independently of each other. As discussed above,the fine-positioning control is desirable to maintain proper verticalregistration of print heads 36 and 42.

Moreover, voice coil mechanisms 52 and 54 may be have additionalutilities beyond toggling print heads 36 and 42 between lowered, activestates and raised, passive states. For example, in some embodiments,voice coil mechanisms 52 and 54 may each be used to compensate forpotential backlash in the coarse, z-axis positioner of the gantry forplaten 14 (shown in FIG. 1). Such positioner backlash may occur due tofrictional resistance in the mechanical mating features of the gantryfor platen 14.

Additionally, voice coil mechanisms 52 and 54 may used in applicationsin which print heads 36 and 42 may require rapid vertical accelerations,such as when reaching ends of tool paths. For example, when print head36 reaches an end of a tool path and the extrusion is halted, voice coilmechanism 52 may rapidly toggle print head 36 upward (e.g., at about 3g-forces) to break off the string of extruded material that mayotherwise trail after the tip of print head 36. Voice coil mechanism 54may function in a similar manner.

In alternative embodiments, the components of voice coil mechanisms 52and 54 that are retained by lower extensions 118 and 120 may vary. Forexample, in one embodiment, front plate 158, rear plate 167, uppermagnets 224 and 226, and lower magnets 228 and 230 may be retained bylower extension 118, thereby allowing these components to move withreceptacle 46. In this embodiment, voice coil 232 may then be retainedby carriage frame 44. A similar arrangement may be used for voice coilmechanism 54 as well. In additional alternative embodiments, one or bothof voice coil mechanisms 52 and 54 may includes ferrofluids or othersimilar compositions having small-scale ferromagnetic or ferrimagneticparticles suspended in carrier fluids (e.g., water and organicsolvents).

Referring to the above-discussed toggling example (see FIGS. 8 and 9),after a given layer of support structure 26 is completed, controller 28may direct voice coil mechanism 54 to raise receptacle 48 and print head42 upward along the vertical z-axis from lowered elevation 164. Toaccomplish this, controller 28 may direct carriage 18 (through controlboard 50) to induce an electrical current through voice coil 238 in afirst rotational direction. The magnetic fields around voice coil 238force voice coil 238 and receptacle 48 (and print head 42) upward, asillustrated by arrow 166 b.

Flexure segment 108 of upper flexure 88 and arms 128 b and 128 d oflower flexure 124 accordingly flex upward along with receptacle 48 andprint head 42 to reach un-flexed and level states. The engagementsbetween base portions 68 and 78 with carriage frame 44 may also defineupper and lower hard stops (i.e., physical stopping points) at raisedelevation 162 and lowered elevation 164. For example, base portion 68(and/or lower extension 118) may be raised upward until contacting adownward-facing member of carriage frame 44 corresponding to raisedelevation 162, and may be lowered downward until contacting anupward-facing member of carriage frame 44 corresponding to lowerelevation 164.

Similarly, base portion 78 (and/or lower extension 120) may be raisedupward until contacting a downward-facing member of carriage frame 44corresponding to raised elevation 162, and may be lowered downward untilcontacting an upward-facing member of carriage frame 44 corresponding tolower elevation 164. Thus, these hard stop locations may correspond toprevent further vertical movement of either print head 36 or 42 aboveraised elevation 162 or below lowered elevation 164. Accordingly, whenthe upper hard stop for base portion 78 is reached, control board 50 mayhold the intensity of the electrical current through voice coil 238.This braces base portion 78 against the upper hard stop, and maintainsthe intended elevation (e.g., raised elevation 162).

Additionally, the second optical encoder assembly (having sensor array222 b, shown in FIG. 5) for receptacle 48 may measure the verticalposition of receptacle 48 and print head 42. This is in comparison to aservo-motor based mechanism, in which receptacle 48 would be servoed toa particular vertical position (rather than being moved to a hard stop,followed by an encoder measurement). The measured vertical position maybe used for a variety of functions, such as for maintaining registrationand for maintaining constant elevations along the vertical z-axis byservoing voice coil mechanism 54 with the measured signals from thesecond optical encoder assembly.

Controller 28 may also direct voice coil mechanism 52 to lowerreceptacle 46 and print head 36 downward along the vertical z-axis fromraised elevation 162. In particular, controller 28 may direct carriage18 (through control board 50) to induce an electrical current throughvoice coil 232 in a first rotational direction. The magnetic fieldsaround voice coil 232 force voice coil 232 and receptacle 46 (and printhead 36) downward, as illustrated by arrow 166 a.

Flexure segment 106 of upper flexure 88 and arms 128 a and 128 c oflower flexure 124 accordingly flex downward along with receptacle 46 andprint head 36. When the lower hard stop for base portion 68 is reached,optical control board 50 may hold the intensity of the current throughvoice coil 232. This braces base portion 68 against the lower hard stop,and maintains the intended elevation (e.g., lowered elevation 164).Additionally, optical encoder assembly 220 may measure the verticalposition of receptacle 46 and print head. The measured vertical positionmay also be used for a variety of functions, such as for maintainingregistration and for maintaining constant elevations along the verticalz-axis by servoing voice coil mechanism 52 with the measured signalsfrom the second optical encoder assembly.

After a given layer(s) of 3D part 24 is completed, controller 28 maythen direct voice coil mechanism 52 to raise receptacle 46 and printhead 36 upward along the vertical z-axis from lowered elevation 164. Toaccomplish this, controller 28 may direct carriage 18 (through controlboard 50) to induce an electrical current through voice coil 232 in asecond rotational direction that is opposite of the first rotationaldirection of the electrical current previously applied to voice coil232. The magnetic fields around voice coil 232 accordingly force voicecoil 212 and receptacle 46 (and print head 36) upward.

Flexure segment 106 of upper flexure 88 and arms 128 a and 128 c oflower flexure 124 accordingly flex upward along with receptacle 46 andprint head 36 to reach un-flexed and level states. When the upper hardstop for base portion 68 is reached, control board 50 may hold theintensity of the electrical current through voice coil 232. This bracesbase portion 68 against the upper hard stop, and maintains the intendedelevation (e.g., raised elevation 162). Additionally, optical encoderassembly 220 may measure the vertical position of receptacle 46 andprint head 36.

Correspondingly, controller 28 may also direct voice coil mechanism 54to lower receptacle 48 and print head 42 downward along the verticalz-axis from raised elevation 162. In particular, controller 28 maydirect carriage 18 (through control board 50) to induce a currentthrough voice coil 238 in a second rotational direction that is oppositeof the first rotational direction of the electrical current previouslyapplied to voice coil 238. The magnetic fields around voice coil 238accordingly force voice coil 238 and receptacle 48 (and print head 42)downward.

Flexure segment 108 of upper flexure 88 and arms 128 b and 128 d oflower flexure 124 accordingly flex downward along with receptacle 48 andprint head 42. When the lower hard stop for base portion 78 is reached,control board 50 may hold the intensity of the electrical currentthrough voice coil 238. This braces base portion 68 against the lowerhard stop, and maintains the intended elevation (e.g., lowered elevation164). Additionally, the second optical encoder assembly may measure thevertical position of receptacle 48 and print head 42.

Due to their independent operations, voice coil mechanisms 52 and 54 mayraise and lower receptacles 46 and 48 at the same time in areciprocating manner, if desired. This reduces the time required totoggle print heads 36 and 42 between build runs. Furthermore, thecombination of voice coil mechanisms 52 and 54, along with upper flexure88 and lower flexure 124 provide precise control of vertical movementfor receptacles 46 and 48, while also preventing unintentionalhorizontal movement of receptacles 46 and 48 (and print heads 36 and 42)relative to carriage frame 44. This allows system 10 to build 3D part 24and support structure 26 with high-resolution features, while alsoallowing print heads 36 and 42 to be readily removed and replaced withnew print heads 36 and 42.

FIG. 15 illustrates a process for inserting or otherwise loading printhead 36 into receptacle 46, which may also be applied to print head 42and receptacle 48. As shown, lid 70 includes circuit board 240 securedto the inside surface of lid 70 with screws 242 or other similarfasteners. Circuit board 240 is a printed circuit board or other similardevice coupled to electrical interface 94 (shown in FIGS. 2-4 and 9),and includes electrical contact 244. Electrical contact 244 isconfigured to interface with print head 36 when print head 36 isinserted into base portion 68 with lid 70 closed. This allows electricalpower and communication to be relayed to and between print head 36 andcontrol board 50 (via circuit board 240, electrical interface 94, andelectrical contact 244) in the same manner as for circuit board 174(shown in FIGS. 10 and 11). As mentioned above, in alternativeembodiments, circuit board 240 may be replaced with different types ofelectrical circuits, such as one or more flexible circuits. In theseembodiments, the flexible circuit may directly connect between controlboard 50 and lid 70 (i.e., electrical interface 94 may be omitted).

As further shown in FIG. 15, cartridge assembly 60 of print head 36includes housing cover 246 and housing body 248, each of which may bemolded or cast from one or more metallic and/or plastic materials.Housing cover 246 is secured to housing body 248 with latch 250, whichis engaged with clip 252 of housing body 248 for assembling print head36. Housing cover 248 includes electrical ports 254, indentation 256,and guide tube ports 258 and 260.

Electrical ports 254 are openings through housing cover 246 that provideaccess to a circuit board within cartridge assembly 60 (not shown inFIG. 15). When lid 70 of receptacle 46 is closed, electrical contact 244inserts through one of electrical ports 254 to engage the circuit boardof print head 36. This arrangement relays electrical power andcommunication to and between circuit board 240 and print head 36.

In the shown embodiment, electrical ports 254 are arranged to provideaccess to multiple electrical contacts (e.g., electrical contact 242),and to accommodate circuit boards (e.g., circuit board 240) havingmultiple electrical contacts. In an alternative embodiment, housingcover 246 may include a single electrical ports 254 configured toreceive electrical contact 244.

Indentation 256 is a downward-facing indentation of housing cover 226that accommodates the geometry of recessed lip 180 of lid 70 when printhead 36 is retained by receptacle 46. For example, recessed lip 180maybe inserted into indentation 256 when lid 70 is closed, which assistsin securing print head 36 to receptacle 46.

Guide tube ports 258 and 260 are openings through housing cover 226 thatprovide access for guide tubes of part or support materials. Forexample, guide tube port 258 may receive guide tube 34 (shown in FIG.1), which extends through guide tube port 258, thereby aligning guidetube 34 with liquefier tube assembly 62 along the vertical z-axis.

In the shown embodiment, guide tube port 260 is an unused opening forprint head 36, which allows a single design for housing cover 246 to beused for both minor image print heads 36 and 42. Accordingly, for printhead 42, guide tube 40 may extend through guide tube port 260, and guidetube port 258 may be an unused opening. In alternative embodiments, theunused guide tube ports (e.g., guide tube port 260 for print head 36)may be omitted.

Housing body 248 is configured to rest on the floor of base portion 68,and includes overhang feature 262 and vent 264. Overhang feature 262 hasa downward converging geometry, and is the portion of cartridge assembly60 that liquefier pump assembly 62 extends downward from when print head36 is mounted in receptacle 46.

As shown above (see e.g., FIGS. 2 and 8), overhang feature 262 and thecorresponding overhang feature of print head 42 have downward converginggeometries that are mirror images of each other. This reduces the riskof inserting the incorrect print head into a given receptacle.Accordingly, in comparison to the housing covers (e.g., housing cover246), housing body 248 and the corresponding housing body of print head42 are mirror images of each other. Vent 264 is a sidewall vent throughhousing body 248 that allows air flow from cooling unit 56 and ventopening 170 to enter print head 36.

Print head 36 may be inserted or otherwise loaded into receptacle 46 bysliding cartridge assembly 60 into base portion 68 (e.g., as indicatedby arrow 266) until the rear portion of cartridge assembly 60 restswithin base portion 68. During the insertion, alignment cones 184 areinserted into the bottom reciprocating slots of housing body 248 (notshown in FIG. 15) to provide a three-point alignment between print head36 and base portion 68. When cartridge assembly 60 is inserted withinbase portion 68, overhang feature 262 and liquefier pump assembly 62extend downward (e.g., as shown above in FIGS. 2, 3, 5, and 8).Additionally, when cartridge assembly 60 is inserted within base portion68, vent 264 is aligned with vent opening 170 in the lateral wall ofbase portion 68. As mentioned above, this alignment allows cooling unit56 (shown above in FIGS. 2, 5, and 8) to direct air flow through ventopening 170 and into print head 36 via vent 264.

After print head 36 is inserted into base portion 68, lid 70 may then beclosed against base portion 68, as discussed above. When lid 70 isclosed, electrical contact 244 engages one of electrical ports 254 ofprint head 36. This arrangement relays electrical power andcommunication to and between circuit board 240 and print head 36.Additionally, when lid 70 is closed and locked to base portion 68, therear portion of cartridge assembly 60 is secured within receptacle 46with the three-point alignment, thereby preventing lateral or verticalmovement of print head 36 relative to receptacle 46 (or roll, pitch, andyaw movements).

Receptacles 46 and 48, having the lid and base portion engagements, areexamples of suitable receptacles for use with carriage frame 44 toretain print heads 36 and 42 with snap-fit mechanisms. In alternativeembodiments, carriage 18 may include a variety of different receptacleshaving snap-fit mechanisms for retaining print heads 36 and 42 in amanner that prevents movement of print heads 36 and 42 relative to theirrespective receptacles.

For example, base portion 68 of receptacle 46 may include a snap-fitengagement in which print head 36 may be inserted into base portion 68and snap fitted (e.g., with a biasing spring from the floor of baseportion 68). In this embodiment, lid 70 may be omitted, and print head36 may be retained by base portion 68 alone with the snap-fitengagement, which prevents print head 36 from moving relative to baseportion 68 (e.g., with alignment cones 184). Electrical connections maythen be made directly between control board 50 and print head 36.

As shown in FIG. 16, housing body 248 also includes bottom surface 268,alignment slots 270 and 272, screw slot 274, and rear pocket 276, whererear pocket 276 is a U-shaped portion of housing body 248 that isconfigured to extend into the U-shaped, rear wall opening 200 of baseportion 68 (shown above in FIGS. 11 and 15). Bottom surface 268 is thesurface that rests on the floor of base portion 68 (shown in FIGS. 2-5and 7-15). Alignment slots 270 and 272 are the reciprocating slots thatengage with alignment cones 184 (shown in FIGS. 10, 11, and 15) tocreate the three-point alignment between print head 36 and base portion68. Screw slot 274 is a slot configured to receive the tip of screw 140when screw 140 extends through opening 188 (shown above in FIGS. 10, 11,14, and 15). This prevents screw 140 from interfering with thethree-point alignment when print head 36 is inserted into base portion68.

The three-point alignment desirably fixes the position of print head 36relative to base portion 68 with respect to the x-y-z coordinates, inaddition to the roll, pitch, and yaw orientations. For example, thecontact between bottom surface 268 and the floor of base portion 68 mayfix the pitch orientation, the engagement between alignment slot 270 (anelongated slot) and one of alignment cones 184 may fix the roll and yaworientations, and the engagement between alignment slot 272 and theother alignment cone 184 may fix the x-y-z coordinates.

As shown in FIG. 17, print head 36 also includes motor 278, where motor278 is fully encased within housing cover 246 and housing body 248.Motor 278 includes motor body 280, mounting plate 282, and gear 284,where mounting plate 282 is a metallic or plastic plate secured to motorbody 280 with screws 286 or other similar fasteners. Mounting plate 282is configured to be inserted in mounting slots 288 of housing body 248,thereby securing motor 278 to cartridge assembly 60 when housing cover246 and housing body 248 are secured together. Housing body 248 alsoincludes mounting slots 289, where mounting slots 288 and 289 arerib-based members of housing body 248.

As further shown, liquefier pump assembly 62 is partially encased withinhousing cover 246 and housing body 248, and extends downward out ofoverhang feature 262, as discussed above. Liquefier pump assembly 62includes drive mechanism 290, backbone assembly 292, liquefier assembly294, and drive block 295, where liquefier pump 294 is encased bybackbone assembly 292, and drive mechanism 290 and drive block 295 areretained by backbone assembly 292 at an upstream location relative toliquefier assembly 294.

Motor body 280 is the drive component of motor 278 that receiveselectrical power from the circuit board of print head 36 (not shown) viaelectrical cables (not shown) for generating rotational power. Gear 284is a rotatable component that is axial connected to motor body 280 toreceive the generated rotational power. Gear 284 correspondingly engagesdrive mechanism 290 to feed successive portions of the part materialfilament through drive block 295 and liquefier assembly 294.

Backbone assembly 292 and liquefier assembly 294 are the portions ofliquefier pump assembly 62 that extend downward from overhang feature262. Backbone assembly 292 is mountable to housing body 248 via mountingslots 289, thereby securing backbone assembly 292 to cartridge assembly60 when housing cover 246 and housing body 248 are secured together.Drive mechanism 290 is retained by backbone assembly 292 within overhangfeature 262, and motor 278 with gear 284 is disposed above and engagedwith drive mechanism 290. Motor body 280 is accordingly mounted in therear portion of cartridge 60 (when housing cover 246 and housing body248 are secured together) with mounting plate 282, such that gear 274extends above overhang feature 262 for engagement with drive mechanism290.

FIGS. 18 and 19 illustrate additional components of cartridge 60. Asshown in FIG. 18, housing cover 246 includes circuit board 296 securedto the inside surface of housing cover 246 with screws 298 or othersimilar fasteners. Circuit board 296 is a printed circuit board or othersimilar device that engages with electrical contact 244 of circuit board240 (shown above in FIG. 15) through electrical ports 254 when lid 70 isclosed against base portion 68. Circuit board 296 is configured to relayelectrical power and communications to and between liquefier pumpassembly 62 and motor 278 (shown above in FIG. 17) with the use ofelectrical cables (not shown).

As shown in FIG. 19, housing body 248 also includes outlet opening 300.Outlet opening 300 is the opening in overhanging portion 262 thoughwhich backbone assembly 292 and liquefier assembly 294 of liquefier pumpassembly 62 (shown above in FIG. 17) extend. Outlet opening 300desirably provides a snug fit with backbone assembly 292 to preventliquefier pump assembly 62 from moving relative to housing body 248.

Housing body 248 may also additional components for retaining theelectrical cables and/or guide tube 34 (shown above in FIG. 1). Forexample, housing body 248 may include a V-shaped feature (not shown)defining a notch to hold and direct guide tube 34 from guide tube port258 (shown above in FIGS. 15 and 17) to liquefier pump assembly 62. Inparticular, guide tube 34 may rest within the notch of the V-shapedfeature, which prevents guide tube 34 from moving around withincartridge assembly 60 during use in system 10 (shown in FIG. 1).Additionally, the electrical cables (not shown) interconnecting circuitboard 256 and liquefier pump assembly 62 may be retained on eitherlateral side of the notch. This prevents the electrical cables frommoving around within cartridge assembly 60 during use in system 10, andreduces the risk of the electrical cables from getting caught by themoving components of liquefier pump assembly 62 (e.g., drive mechanism290).

As shown in FIG. 20, motor 278 also includes thrust bearings 302 andmagnet 304, and gear 284 includes threaded surface 306. Thrust bearings302 are disposed between mounting plate 282 and a shoulder of gear 284.During operation, the rotation of gear 284 may apply an axial thrustload in the direction of arrow 308 depending on the rotational directionof gear 284. Thrust bearings 302 are positioned to absorb the axialthrust loads applied to gear 284, which reduce the risk of damage tomotor body 280 during operation.

Magnet 304 is a rotatable magnet located on the opposing end of motorbody 280 from gear 284, and is also axially connected to motor body 280to rotate with gear 284. When motor 278 is mounted in housing body 248,magnet 304 is positioned in rear pocket 276. As discussed above, whenprint head 36 is mounted in receptacle 46, rear pocket 276 extends intorear wall opening 200 (shown above in FIGS. 11 and 15), therebypositioning magnet 304 in close proximity to encoder sensor 204 (shownin FIG. 11) regardless of the vertical toggle elevation of print head36.

Encoder sensor 204 is a first component of an encoder assemblyconfigured to measure the rotation of gear 284. Magnet 304 is a secondcomponent of the encoder assembly, where encoder sensor 204 is capableof measuring the rotational angle of magnet 304 as magnet 304 rotateswith gear 284. This arrangement allows the rotational rate and directionof gear 284 to be monitored, which corresponds to the rate at which thepart material filament is fed through liquefier pump assembly 62. Asmentioned above, encoder sensor 204 is connected control board 50 (shownabove in FIGS. 2-5, 8 and 9) for communicating with controller 28 (shownabove in FIG. 1).

FIGS. 21-25 further illustrate liquefier pump assembly 62 in use withguide tube 34. In the shown embodiment, liquefier pump assemblies 62 and66 are mirror images of each other. As such, the following discussion ofthe various subcomponents of liquefier pump assembly 62 may also applyto liquefier pump assembly 66, which may be engaged with guide tube 40for extruding the support material from the support material filament.

As shown in FIG. 21 and as mentioned above, liquefier pump assembly 62includes drive mechanism 290, backbone assembly 292, liquefier assembly294, and drive block 295, where liquefier assembly 294 includesliquefier 310. Backbone assembly 292 is a structure component ofliquefier pump assembly 64 and includes backbone plate 312 and heatshield 314.

Backbone plate 312 is a first metallic member (e.g., a steel stampedplate) that is shaped to be secured to heat shield 314 and to retaindrive mechanism 290. As shown, backbone plate 312 includes shaft portion316 (extending along the back side of heat shield 314, best shown belowin FIG. 22), angled shield 318, retention arms 320 and 322, and tabs323. Shaft portion 316 extends along the vertical z-axis between angleshield 318 and tip end 62 a, and is secured (e.g., welded) to heatshield 314. For example, shaft portion 316 includes a pair of tabs 324adjacent to tip end 62 a (only a single tab 324 is shown in FIG. 21),which are suitable for aligning and bracing heat shield 314 with shaftportion 316 for welding heat shield 314 and shaft portion 316 together.

Angled shield 318 has a downward converging surface that corresponds tothe downward converging geometry of overhang feature 262 (shown above inFIGS. 15-17, and 19) providing a mating fit between angled shield 318and overhang feature 262 when liquefier pump assembly 62 is mounted inhousing body 248 (shown above in FIGS. 15-17, and 19). Angled shield 318may also function as a heat shield to restrict the air flow from vent264 (shown above in FIGS. 15-17 and 19) to a pathway within heat shield314 and shaft portion 316, as discussed below. Retention arms 320 and322 are laterally-extending arms from angle shield 318 that providesuitable locations for supporting drive mechanism 290 and drive block295 upstream from liquefier assembly 294. Tabs 323 are the components ofbackbone assembly 292 that are configured to be inserted into mountingslots 289 of housing body 248 (shown above in FIG. 17) for mountingbackbone assembly to housing body 248.

Heat shield 314 is second metallic member (e.g., a steel stamped plate)that is secured to shaft portion 316, as mentioned above. This defines acentral conduit along the vertical z-axis through which liquefierassembly 294 extends.

As further shown, backbone plate 312 also includes inlet vent 326 (bestshown in FIG. 22), heat shield 314 also includes inlet vent 328, and theengagement between heat shield 314 and angled shield 318 define inletvent 330 (best shown in FIG. 25). Inlet vents 326, 328, and 330 allowthe air flow from cooling unit 56 (shown above in FIGS. 2, 3, 5, and 8)that is directed through cartridge 60 (e.g., shown above in FIG. 15) toenter the central conduit between heat shield 314 and shaft portion 316.

Heat shield 314 and shaft portion 316 collectively include vents 62 b,which, in the shown embodiment, are rectangular openings in heat shield314 and shaft portion 316 above liquefier 310 of liquefier assembly 294.The air flow that passes through the central conduit between heat shield314 and shaft portion 316 thereby exits print head 36 through vents 62b. Directing the air flow through print head 36 in this manner allowsthe air flow to cool the components within cartridge 60 (e.g., motor278, shown above in FIGS. 17 and 20). In addition, the air flow alsofollows the feed path of the part material filament through liquefierpump assembly 62 prior to reaching liquefier 310. This reduces the riskof having the part material filament melting upstream from liquefier310, which allows the part material filament to provide a viscosity-pumpaction to extrude the part material from liquefier 310. Otherwise,without the air flow through the central conduit in this manner, thepart material filament may undesirably heat up and soften at locationsupstream from liquefier 310, which could impair the extrusion propertiesof liquefier pump assembly 62.

One or more of inlet vents 326, 328, and 330 may also function as inletopenings for the electrical cables (not shown) that interconnect circuitboard 296 (shown above in FIG. 18) and liquefier assembly 294. Forexample, the electrical cables may extend through outlet opening 300(shown above in FIG. 19), through inlet vent 326, and down through thecentral conduit to liquefier assembly 310. This arrangement reduces therisk of the electrical cables from getting entangled in drive mechanism290.

As shown in FIGS. 21 and 22, drive mechanism 290 is configured to feedsuccessive portions of the part material filament (not shown) from guidetube 34 to liquefier assembly 294. Drive mechanism 290 includes capstangear 332 and bearing block 334, which are located adjacent to driveblock 295, upstream from liquefier assembly 294. As used herein, theterms “upstream” and “downstream” are made with reference to a filamentfeed direction along arrow 336. As further shown, drive block 295includes seal ring 338. Capstan gear 332, bearing block 334, and driveblock 295 may each be molded or cast from one or more metallic and/orplastic materials. Seal ring 338 may be fabricated from one or moreplastic and/or rubber-based materials.

Capstan gear 332 is operably supported by bearing block 334 and driveblock 295, which are respectively retained by retention arms 320 and322. Capstan gear 332 includes perimeter teeth 340, which are gear teethor an otherwise textured surface that extend around the outer perimeterof capstan gear 332, and are the portion of drive mechanism 290 thatengage with threaded surface 306 of gear 284 (shown above in FIG. 20).

As discussed below, drive block 295 is the component through which thepart material filament passes while being fed from guide tube 34 toliquefier assembly 294. Guide tube 34 engages drive block 295 at sealring 338, where seal ring 338 is a moisture seal that desirablyrestricts or prevents moisture from entering guide tube 34 and driveblock 295.

As further shown in FIG. 22, backbone plate 314 includes slot 342through which capstan gear 332 extends. Additionally, shaft portion 316includes clasp 344, which is a clasp member on the interior side ofshaft portion 316 for retaining the electrical cables (not shown) thatinterconnect circuit board 296 and liquefier assembly 294.

As shown in FIG. 23, drive mechanism 290 also includes drive shaft 346,which extends through and is secured to an axial opening of capstan gear332 (referred to as axial opening 348). In particular, drive shaft 346includes outer surface 350, which may be secured within axial opening348, such as with frictional fitting, welding, adhesives, and the like.This allows the rotation of capstan gear 332 to correspondingly rotatedrive shaft 346. In an alternative embodiment, capstan gear 332 anddrive shaft 346 may be fabricated as a single component in which driveshaft 346 extends from the rotational axis of capstan gear 332.

Drive shaft 346 may also be molded or cast from one or more metallicand/or plastic materials. Drive shaft 346 also includes first end 352and second end 354, where first end 352 extends into bearing block 334,and second end 354 extends into drive block 295 at lateral opening 356.This mounts drive shaft 346 (and capstan gear 332) to bearing block 334and drive block 295, which allow drive shaft 346 and capstan gear 332 tofreely rotate under the rotational power from gear 284 (shown in FIGS.17 and 20).

Drive shaft 346 also includes toothed surface 358, which is a toothed orotherwise textured surface that also extends into lateral opening 356 ofdrive block 295, and is the rotatable surface that engages the partmaterial filament to feed the part material filament downward intoliquefier assembly 294. Drive block 295 also includes top opening 360,which is the opening in which guide tube 34 (shown in FIGS. 1, 21, and22) and seal ring 338 are connected for feeding the part materialfilament through drive block 295. In particular, seal ring 338 may beinserted into top opening 360, and guide tube 34 may then be insertedinto and secured to top opening 360, such as with frictional fitting,adhesives, and the like.

In the shown embodiment, liquefier assembly 294 includes liquefier 310(as mentioned above), filament tube 362, and extrusion tip 364. Filamenttube 362 includes top end 366, which engages a bottom opening of driveblock 295 (not shown in FIG. 23) and bottom end 368, which extends intoliquefier 310. Examples of suitable liquefier assemblies for liquefierassembly 294 (e.g., liquefier 310, filament tube 362, and extrusion tip364) include those disclosed in Swanson et al., U.S. patent applicationSer. No. 12/888,087, entitled “Liquefier Assembly For Use InExtrusion-Based Additive Manufacturing Systems”; Swanson et al., U.S.patent application Ser. No. 12/888,098, entitled “Method For BuildingThree-Dimensional Models With Extrusion-Based Additive ManufacturingSystems”; Batchelder et al., U.S. Application Publication No.2009/0273122; Swanson et al., U.S. Pat. No. 6,004,124; Comb, U.S. Pat.No. 6,547,995; and LaBossiere et al., U.S. Pat. Nos. 7,384,255 and7,604,470. As discussed in these references, the part material filamentmay be fed through filament tube 362 into liquefier 310. Liquefier 310may then melt and extrude the part material from extrusion tip 364 build3D part 24 (shown in FIG. 1). In some embodiments, extrusion tip 364 isintegrally formed with liquefier 310.

As shown in FIG. 24, heat shield 314 also includes bottom surface 370,which is desirably secured to shaft portion 316 (e.g., welded). Bottomsurface 370 includes opening 372 through which extrusion tip 364 extendsthrough. In the shown embodiment, bottom surface 370 includes radialtabs 374, which extend inward into opening 372 and provide suitablelocations for securing extrusion tip 374 (e.g., with spot welding).Liquefier 310 (shown above in FIGS. 17 and 21-23) is desirably notdirectly connected to backbone assembly 292 to reduce heat transferbetween liquefier 310 and heat shield 314 and shaft portion 316. Assuch, securing extrusion tip 364 to bottom surface 370 in this mannerprevents liquefier assembly 294 from moving relative to backboneassembly 292.

In addition, this arrangement also reduces heat transfer from extrusiontip 364 to backbone assembly 292 by reducing the contact surface areabetween extrusion tip 364 and bottom surface 370 to radial tabs 374(e.g., three small tabs). This allows liquefier 310 to maintain asuitable thermal profile during operation. If extrusion tip 364 wereotherwise secured to bottom surface 370 around the entire perimeter ofextrusion tip 364, the heat transfer would be higher, thereby requiringliquefier 310 to compensate to account for the thermal loss.

Furthermore, bottom surface 370 may be laminated or otherwise coatedwith a film of one or more materials having low coefficients offriction, such as fluorinated polymers (e.g., perfluoropolymers).Examples of suitable fluorinated polymers includepolytetrafluoroethylenes (PTFE), fluorinated ethylene propylenes, andperfluoroalkoxy polymers. Examples of suitable commercially availablefluorinated polymers include PTFE available under the trade designation“TEFLON” from E.I. du Pont de Nemours and Company, Wilmington, Del. Theuse of the film or coating in this manner prevents or otherwise reducesthe part material from sticking to bottom surface 370 during a build runand/or during purge and extrusion tip cleaning steps.

As shown in FIG. 25, drive block 295 also includes bottom opening 376and channel 378, where bottom opening 376 is the outlet opening of driveblock 295 in which top end 366 of filament tube 362 extends into.Channel 378 interconnects top opening 360 and bottom opening 376, and isa pathway extending along the vertical z-axis in which toothed surface358 of drive shaft 346 extends for engaging the part material filament(not shown).

Channel 378 may have dimensions that accommodate the part materialfilament without undue friction, while desirably preventing the partmaterial filament from buckling while engaged with toothed surface 358of drive shaft 346. Accordingly, channel 378 includes a lateral port(not shown) at the intersection with lateral opening 256 (shown above inFIG. 23) through which toothed surface 358 extends. Channel 378 alsoincludes lateral supporting wall 380, which functions as a bracing wallfor supporting the part material filament as toothed surface 358 engagesthe part material filament.

The engagement between guide tube 34, drive block 295, and filament tube362, along with drive shaft 346 extending through lateral opening 356,provides a self-alignment feature that reduces or prevents the risk ofmisfeeding the part material filament into liquefier tube 362 andliquefier 310. If drive block 295 were otherwise omitted, a gap wouldexist between guide tube 34 and filament tube 362 at the location ofchannel 378. This gap could potentially result in misfeeds of the partmaterial filament from guide tube 34 to filament tube 362, which couldresult in delays in building 3D part 24. Furthermore, having the leadingend of the part material filament extending at least into drive block295, and even into filament tube 362, further increases theself-alignment feature of liquefier pump assembly 62.

Prior to operation, the part material filament may reside in guide tube34, and desirably extends at least as far downward into drive block 295as conduit 378 for engagement with toothed surface 358. This allowsdrive mechanism 290 to readily feed the part material filament withoutrequiring additional feeding steps.

After print head 36 is inserted into receptacle 46, cooling unit 56 maydirect air flow through cartridge assembly 60 and downward intoliquefier pump assembly 62. As discussed above, the air flow is directeddownward through the central conduit between backbone plate 312 and heatshield 314, and out of the vents (e.g., vents 62 b).

Controller 28 may then direct motor 278 to rotate gear 284 (e.g., viacontrol board 50, electrical interfaces 94 and 98, circuit board 240,electrical contact 244, electrical ports 254, circuit board 296, and therespective electrical connections, such as electrical cables). Theengagement between threaded surface 306 of gear 284 and toothedperimeter 340 of capstan gear 332 correspondingly rotates capstan gear332, such as in the direction of arrow 382. The secured connectionbetween outer surface 350 of drive shaft 346 and axial opening 348 ofcapstan gear 332 correspondingly rotates drive shaft 346 in therotational direction of arrow 382 at the same angular rate as capstangear 332. This accordingly rotates toothed surface 358 in the rotationaldirection of arrow 382 at the same angular rate as capstan gear 332.

The rotation of toothed surface 358 in the rotational direction of arrow382 causes the teeth of toothed surface 358 to engage with the partmaterial filament within channel 378, where the part material filamentis also braced against lateral supporting wall 380. The engaged partmaterial filament is then driven downward into filament tube 362 andliquefier 310, in the direction of arrow 336. Within liquefier 310, thepart material filament is melted and extruded out of extrusion tip 364to build 3D part 24, for example, as disclosed in Swanson et al., U.S.patent application Ser. No. 12/888,087, entitled “Liquefier Assembly ForUse In Extrusion-Based Additive Manufacturing Systems”; and Swanson etal., U.S. patent application Ser. No. 12/888,098, entitled “Method ForBuilding Three-Dimensional Models With Extrusion-Based AdditiveManufacturing Systems”.

The upstream segments of the part material filament provide aviscosity-pump action to extrude the molten part material from extrusiontip 364 based on the feed rate of the part material filament intoliquefier 310. The feed rate of the part material filament iscorrespondingly based on the drive rates of gear 284 of motor 278,capstan gear 332, and drive shaft 346.

When the extrusion run with liquefier pump assembly 62 is completed,controller 28 may direct motor 278 to stop the rotate of gear 284, whichcorrespondingly stops the rotations of capstan gear 332 and drive shaft346. This halts the feeding of the part material filament into liquefier310, which correspondingly stops the extrusion of the molten partmaterial from extrusion tip 364.

Receptacle 42 and print head 36 may then be toggled upward with voicecoil mechanism 52, and receptacle 48 and print head 42 may be toggleddownward with voice coil 54, as discussed above. Controller 28 may thendirect print head 42 to extrude the molten support material fromliquefier pump assembly 66 in the same manner as discussed above forliquefier pump assembly 62. The extrusion runs and toggling between thelowered, active states and the raised, passive states may then berepeated to build 3D part 24 and support structure 26 in a layer-basedmanner pursuant to the fused deposition modeling technique.

FIG. 26 is a flow diagram of method 400 for assembling print heads 36and 42. The following discussion on method 400 is made with reference toprint head 36 with the understanding that method 400 may also apply toprint head 42. As shown, method 400 includes steps 402-416, andinitially involves assembling liquefier pump assembly 62 (step 402). Anexample of a suitable method for assembling liquefier pump assembly 62pursuant to step 402 is discussed below. Liquefier pump assembly 62 maythen be mounted in housing body 248 of cartridge assembly 60 (step 404).For example, backbone assembly 292 and liquefier assembly 294 may beinserted through opening 300 in housing body 248, tabs 323 may beinserted into mounting slots 289, and angled plate 318 may be supportedby overhang feature 262 of housing body 248.

In an alternative embodiment, liquefier pump assembly 62 may be onlypartially assembled prior to being mounted in housing body 248. Forexample, in one embodiment, drive mechanism 290 and drive block 295 maybe mounted onto retention arms 320 and 322 of backbone assembly 292after mounting liquefier pump assembly 62 in housing body 248.

Motor 278 may then be mounted in housing body 248 (step 406). Asdiscussed above, mounting plate 282 of motor 278 may be inserted intomounting slots 288 of housing body 248. This also engages threadedsurface 306 of gear 284 (of motor 278) with teethed perimeter 340 ofcapstan gear 332 to allow gear 284 to rotate capstan gear 332 and driveshaft 346. Additionally, mounting motor 278 in housing body 248positions magnet 304 into rear pocket 276.

Circuit board 296 may also be secured to the inner surface of housingcover 246, such as with screws 298 (step 408). Circuit board 286 maythen be electrically connected to motor 278 and liquefier assembly 294,such as with electrical cables (step 410). In alternative embodiments,steps 408 and 410 may be performed prior to or along with each other andany of steps 402, 404, and/or 406.

Guide tube 34 may also be inserted through guide tube port 258 (step412) and into top opening 360 of drive block 295 to secure guide tube 34to liquefier pump assembly 62 (step 414). As discussed above, thiscreates a self-aligning feature and a moisture barrier for feedingsuccessive segments of the part material filament from guide tube 34 toliquefier 310. Additionally, the part material filament is desirablyinserted at least as far as channel 378 of drive block 295 to engagewith toothed surface 358 of drive shaft 346, which allows the partmaterial filament to be readily used when print head 36 is inserted intoreceptacle 46. Housing cover 246 may then be secured to housing body 248(step 416). This provides print head 36, which is then ready forinsertion into receptacle 46 for use in system 10, as discussed above.

FIG. 27 is a flow diagram of method 418 for assembling liquefier pumpassembly 62, pursuant to step 402 of method 400 (shown above in FIG.26). As shown in FIG. 27, method 418 includes steps 420-430, andinitially involves assembling backbone assembly 292 (step 420). Forexample, backbone plate 312 and heat shield 314 may be fabricated (e.g.,stamped) and welded together with the use of tabs 324.

Liquefier assembly 294 may then be assembled and inserted into backboneassembly 292 (step 422). For example, liquefier assembly 294 may beinserted into backbone assembly 292 such that top end 366 of filamenttube 362 is located adjacent to angled plate 318 and liquefier 310 isdisposed at tip end 62 a. This arrangement also allows extrusion tip 364to extend through opening 372 of bottom surface 370 (of heat shield314).

Extrusion tip 364 may then be spot welded or otherwise secured to radialtabs 374 to secure extrusion tip 364 to backbone assembly 292 (step424). As discussed above, spot welding extrusion tip 364 to radial tabs374 reduces the contact surface area between extrusion tip 364 andbackbone assembly 292 to reduce heat transfer.

Drive shaft 346 may also be inserted into and secured to axial opening348 of capstan gear 332 (step 426) to allow the rotation of capstan gear332 to likewise rotate drive shaft 346. Drive shaft 346 may then beinserted into bearing block 334 and drive block 295 (step 428). Forexample, first end 352 of drive shaft 346 may be inserted into bearingblock 334, and second end 354 may be inserted into lateral opening 356of drive block 295. This rotatably suspends drive shaft 346 (and capstangear 332) between block 334 and drive block 295. Additionally, thisarrangement also positions toothed surface 358 of drive shaft 346 inchannel 378 of drive block 295 to engage a part material filament.

Bearing block 334 and drive block 295 may then be respectively mountedand secured to retention arms 320 and 322 (step 430), and seal ring 338may be inserted into top opening 360 of drive block 295. This step alsoinserts and secures top end 366 of filament tube 362 into bottom opening376 of drive block 295, thereby providing the self-aligning feature forthe part material filament. In alternative embodiments, one or both ofsteps 426 and 428 may be performed prior to or along with steps 410,422, and/or 424. As indicated above in step 402 of method 400, aftermethod 418 is completed, the resulting liquefier pump assembly 62 maythen be mounted in housing body 248, pursuant to step 404 of method 400.

As discussed above, after methods 400 and 418 are completed for each ofprint heads 36 and 42, print heads 36 and 42 may be inserted into andlocked with receptacles 46 and 48 of carriage 18 (and thereby providingprint head assembly 43). System 10 may then be controlled to extrude anddeposit part and support materials from print heads 36 and 42 ontoplaten 14 to build 3D models (e.g., 3D model 24) and support structures(e.g., support structure 26) in a layer-based manner using the fuseddeposition modeling technique.

Furthermore, receptacles 46 and 48 themselves are suspended by carriageframe 44 in a manner that allows controlled movement of receptacles 46and 48 (and print heads 36 and 42) relative to carriage frame 44 alongthe vertical z-axis via voice coil mechanisms 52 and 54, while alsopreventing movement of receptacles 46 and 48 (and print heads 36 and 42)relative to carriage frame 44 in the horizontal x-y plane, as well aspreventing roll, pitch, and yaw movements. This arrangement allows voicecoil mechanisms 52 and 54 to toggle receptacles 46 and 48 (and printheads 36 and 42) between lowed, active states and raised, passive statesin a manner provide precise control of vertical movement for receptacles46 and 48, independently of each other. As such, print head assembly 43is suitable for building 3D models (e.g., 3D model 24) and supportstructures (e.g., support structure 26) with high-resolution features,while also allowing multiple print heads (e.g., print heads 36 and 42)to be replacably interchanged.

As mentioned above, suitable part and support materials for use withsystem 10 and print head assembly 43 include part and support materialfilaments. Suitable part materials for building 3D model 24 includepolymeric and metallic materials. In some embodiments, suitable modelingmaterials include materials having amorphous properties, such asthermoplastic materials, amorphous metallic materials, and combinationsthereof. Examples of suitable thermoplastic materials for the partmaterial filament include acrylonitrile-butadiene-styrene (ABS)copolymers, polycarbonates, polysulfones, polyethersulfones,polyphenylsulfones, polyetherimides, amorphous polyamides, modifiedvariations thereof (e.g., ABS-M30 copolymers), polystyrene, and blendsthereof. Examples of suitable amorphous metallic materials include thosedisclosed in Batchelder, U.S. Patent Application Publication No.2009/0263582.

Suitable support materials for building support structure 26 includepolymeric materials. In some embodiments, suitable support materialsinclude materials having amorphous properties (e.g., thermoplasticmaterials) and that are desirably removable from the correspondingmodeling materials after 3D model 24 and support structure 26 are built.Examples of suitable support materials include water-soluble supportmaterials commercially available under the trade designations “SR10”,“SR20”, and “SR30” Soluble Supports from Stratasys, Inc., Eden Prairie,Minn.; break-away support materials commercially available under thetrade designation “BASS” from Stratasys, Inc., Eden Prairie, Minn., andthose disclosed in Crump et al., U.S. Pat. No. 5,503,785; Lombardi etal., U.S. Pat. Nos. 6,070,107 and 6,228,923; Priedeman et al., U.S. Pat.No. 6,790,403; and Hopkins et al., U.S. Patent Application PublicationNo. 2010/0096072.

In some embodiments, the part and support material filaments may eachhave a cylindrical or substantially cylindrical geometry, such as thosedisclosed in Swanson, U.S. Patent Application Publication No.2010/0283172; Swanson, International Publication No. WO2009/088995;Swanson et al., U.S. Pat. No. 6,923,634; Comb et al., U.S. Pat. No.7,122,246; and Taatjes et al, U.S. Patent Application Publication Nos.2010/0096485 and 2010/0096489.

In alternative embodiments, the part and support material filaments mayeach have a non-cylindrical geometry, such as the ribbon filamentsdisclosed in Batchelder et al., U.S. patent application Ser. No.12/612,333, entitled “Non-Cylindrical Filaments for use inExtrusion-Based Digital Manufacturing Systems”. In these embodiments,suitable liquefiers for liquefier 310 include those disclosed inBatchelder et al., U.S. patent application Ser. No. 12/612,329, entitled“Ribbon Liquefier for use in Extrusion-Based Digital ManufacturingSystems” and in Swanson et al., U.S. patent application Ser. No.12/888,087, entitled “Liquefier Assembly For Use In Extrusion-BasedAdditive Manufacturing Systems”.

In additional embodiments, the part and support material filaments mayeach include topographical surfaces patterns (e.g., tracks) for engagingdrive mechanism 290, as disclosed in Batchelder et al., U.S. patentapplication Ser. No. 12/612,342, entitled “Consumable Materials havingTopographical Surface Patterns for use in Extrusion-Based DigitalManufacturing Systems. Furthermore, the part and support materialfilaments may each include encoded markings, as disclosed in Batchelderet al., U.S. patent application Ser. No. 12/622,042, entitled“Consumable Materials having Encoded Markings for use with DigitalManufacturing Systems and in Batchelder et al., U.S. patent applicationSer. No. 12/949,898, entitled “Encoded Consumable Materials and SensorAssemblies for use in Additive Manufacturing Systems”.

Although the present disclosure has been described with reference topreferred embodiments, workers skilled in the art will recognize thatchanges may be made in form and detail without departing from the spiritand scope of the disclosure.

The invention claimed is:
 1. A print head assembly for use in a fuseddeposition modeling system, the print head assembly comprising: acarriage frame configured to be retained by a gantry mechanism of thefused deposition modeling system; a control board secured to thecarriage frame; a receptacle for use with a removable print head havinga cartridge assembly, a motor gear disposed within the cartridgeassembly, and a filament drive mechanism, wherein the receptaclecomprises: a base portion supported from the carriage frame andconfigured to receive the cartridge assembly of the removable printhead, wherein the base portion comprises an alignment feature configuredto engage with a reciprocal alignment feature of the received cartridgeassembly; and a lid configured to close against the base portion toretain the received cartridge assembly at least partially within thereceptacle; and a rotary encoder retained by the control board, therotary encoder being configured to measure rotations of the motor gearthrough the cartridge assembly while the cartridge assembly is retainedby the receptacle.
 2. The print head assembly of claim 1, and furthercomprising: a lid electrical circuit retained by the lid; an electricalcontact connected to the lid electrical circuit and configured to engagethe received print head when the lid is closed against the base portion.3. The print head assembly of claim 2, wherein the control board has acontrol board interface, and wherein the lid electrical circuit isconfigured to communicate with the control board interface.
 4. The printhead assembly of claim 1, wherein the lid comprises: at least one latchclamp configured to engage the base portion when the lid is closedagainst the base portion; and a pinch actuator configured to disengagethe at least one latch clamp from the base portion.
 5. The print headassembly of claim 1, and further comprising at least one togglemechanism configured to move the receptacle relative to the carriageframe.
 6. The print head assembly of claim 5, wherein the receptacles issupported from the carriage frame with at least one flexure memberconfigured to restrict movement of the receptacle relative to thecarriage frame to directions substantially along a single axis.
 7. Aprint head assembly for use in a fused deposition modeling system, theprint head assembly comprising: a carriage frame configured to beretained by a gantry mechanism of the fused deposition modeling system;a control board secured to the carriage frame; a receptacle for use witha removable print head having a cartridge assembly, a motor geardisposed within the cartridge assembly, a filament drive mechanism, anda liquefier pump assembly, the receptacle comprising: a base portionsupported from the carriage frame and is configured to receive thecartridge assembly of the removable print head, wherein the base portioncomprises an alignment feature configured to engage with a reciprocalalignment feature of the received cartridge assembly; and a lidconfigured to close against the base portion to retain the receivedcartridge assembly at least partially within the receptacle, and suchthat the liquefier pump assembly is located outside of the receptacle;and a rotary encoder retained by the control board, the rotary encoderbeing configured to measure rotations of the motor gear through thecartridge assembly while the cartridge assembly is retained by thereceptacle.
 8. The print head assembly of claim 7, and furthercomprising: a lid electrical circuit retained by the lid; an electricalcontact connected to the lid electrical circuit and configured to engagean electrical port of the received cartridge assembly when the lid isclosed against the base portion.
 9. The print head assembly of claim 8,and further comprising a lid electrical interface connected to the lidon an opposing side of the lid electrical circuit from the electricalcontact.
 10. The print head assembly of claim 9, wherein the controlboard has a control board interface, and wherein the lid electricalcircuit is configured to communicate with the control board interfacevia the lid electrical interface.
 11. The print head assembly of claim7, wherein the receptacle is supported from the carriage frame with atleast one suspension mechanism that is configured to restrict movementof the receptacle relative to the carriage frame to directionssubstantially along a single axis of the at least one axis.
 12. Theprint head assembly of claim 11, and further comprising a togglemechanism configured to move the receptacle relative to the carriageframe along the at least one axis.